Around the start of each month, MiLB.com staff will break down the state of all 30 organizations with updates on their top prospects, Minor League affiliates and more in a new feature called "Farm system storylines."
AL East
Baltimore Orioles
A fourth-round pick out of a New Hampshire high school in 2015, Ryan McKenna hadn't stood out much in his first three seasons in the Orioles system. Now with Class A Advanced Frederick, the 5-foot-11 outfielder did all he could to change that in May. McKenna led all Carolina League batters with a .397 average over 28 games and added a .470 OBP, .586 slugging percentage and 15 extra-base hits. In a bit of a surprise, the 21-year-old did not swipe a base last month, despite speed being his most prominent tool. But with the way McKenna is swinging the bat, he's making himself known in the O's system and now slots into the No. 29 spot in MLB.com's ranking of Baltimore prospects. If his June is anything like his May, he'll surge even higher when that list is updated in the middle of the season. -- Sam Dykstra
Boston Red Sox
Upper-level pitching didn't seem like it would be a strength of the Red Sox system to open 2018. In fact, MiLB.com ranked its pitching depth as 19th-best in Minor League Baseball, and that had much to do with the presence of Jay Groome, who has since undergone Tommy John surgery. However, Jalen Beeks is doing his best to single-handedly change that perception. Boston's No. 15 prospect led all Triple-A pitchers with 43 strikeouts in 36 2/3 innings at Pawtucket in May. He also posted a 3.19 ERA and 0.98 WHIP over his six starts -- signs that he's closer to Fenway Park than ever. With at least six K's in each of his 10 starts and no more than four earned runs allowed in any outing, Beeks has a case to be considered one of the International League's most consistent starters in 2018. After he was added to the 40-man roster last offseason, the 24-year-old southpaw should be considered for a Major League start before the summer's out, especially with Drew Pomeranz's ERA growing to 6.81. -- SD
New York Yankees
This time last year, few knew where Garrett Whitlock would fall in the Draft as an eligible sophomore out of the University of Alabama-Birmingham. The Yankees grabbed him in the 18th round and signed him for $247,500, and after a low-level pitching crunch forced him to open the season at Class A Charleston, the 21-year-old right-hander is forcing his way into New York's plans. Whitlock was promoted to Class A Advanced Tampa on May 14 after posting a 1.13 ERA and 0.75 WHIP with 44 strikeouts over 40 innings in the South Atlantic League. He didn't allow an earned run in either of his first two Tampa starts, striking out 12 and walking three in 8 2/3 frames. Whitlock's stock was relatively low this time last year because of a back injury, but he's been able to break through thanks to a plus fastball, above-average slider and impressive control. A college arm dominating Class A isn't usually much cause for excitement, but the way Whitlock has taken off should raise some eyebrows. -- SD
Tampa Bay Rays
Nathaniel and Brandon Lowe aren't related, though they both call the Tampa Bay farm system home and finished among the top 50 Minor Leaguers in OPS in May. Nathaniel posted a .356/.442/.611 line with five homers, a 14/14 K/BB ratio and a 1.053 OPS in 24 games for Class A Advanced Charlotte, and was rewarded with a spot on the Florida State League All-Star team. Brandon hit .316/.440/.561 with four homers, a triple, 10 doubles and a 1.001 OPS in 27 games with Double-A Montgomery. At No. 14, the latter is the only one of the two ranked by MLB.com among the Rays' top 30 prospects, but with No. 10 Josh Lowe, who is Nathaniel's brother, also in the mix, the Rays should be high on their depth of Lowes right now. -- SD
Toronto Blue Jays
Though his exploits have been well-document, the excellence of Vladimir Guerrero Jr. was clearly the storyline in May. MLB.com's No. 2 prospect hit .438 with nine homers, 10 doubles, 28 RBIs and a 1.248 OPS over 29 games with Double-A New Hampshire. (No one else had an average higher than .421 among qualified Minor Leaguers.) His 1.248 OPS beat his nearest competitor by 22 points, and it's worth noting that two of the four Minor Leaguers to post an OPS above 1.200 play at the hitting factory that is Class A Advanced Lancaster. Guerrero had no such advantage in the Eastern League, but his 86 total bases topped top Brewers prospect Keston Hiura's 81 in second place. (Hiura, featured below, was promoted to Double-A as a result of his hot month.) The punctuation on every one of Guerrero's stats is that he's done it all at just 19. The Jays continue to crow that Guerrero needs to work on his defense at the hot corner, and while that may be true, there simply isn't any offensive challenge left for him at Double-A. -- SD
Video: Guerrero strokes two-run homer for Fisher Cats
AL Central
Chicago White Sox
After injury and a slow start plagued his April, Eloy Jiménez let it rip in May. Baseball's No. 3 overall prospect posted a .374/.419/.664 slash line with six homers and 25 RBIs in 26 games. And that even includes a 6-for-33 (.182) eight-game stretch. Jimenez tallied 14 multi-hit efforts in the month while slugging a grand slam exactly one year and one day after his last four-run jack. The 21-year-old's well-above-average power continues to be showcased as his 10 long balls through 38 games are on pace to surpass his career high of 19. But with that uptick of power, Jimenez has actually cut his strikeout percentage a little this season, leaving fans to wonder what's keeping him from Triple-A. -- Kelsie Heneghan
Cleveland Indians
While Shane Bieber grabbed headlines last season, May was when baseball really got Bieber Fever. After posting a 1.16 ERA in 31 innings over five starts for Double-A Akron in April, the right-hander got the call to Triple-A and continued his upward trajectory. Bieber notched a 1.05 ERA in 34 1/3 innings over five starts with Columbus, highlighted by a seven-inning no-hitter in his final Minor League outing. The Indians were so impressed, they tapped their No. 3 prospect to make his Major League debut on May 31 -- his 23rd birthday. Arguably the most exciting part of Bieber's game is his control. In 65 1/3 Minor League innings this year, he's issued just three walks. In fact, in 262 2/3 career innings, he has 15 walks. This continued when he got to "The Show" with one walk over 5 2/3 innings in his debut. -- KH
Detroit Tigers
Christin Stewart has been one of the most talked-about hitters in the Tigers system since he was selected in the first round of the 2015 Draft. While he isn't the most highly graded player, his power has always exceeded expectations. And after a relatively quiet April that included just four homers, he put on a show in May. Stewart left the yard nine times to climb atop the International League and all Tigers in both the Majors and Minors. The 24-year-old saw his average slip and strikeout total rise last month, but Triple-A Toledo manager Doug Mientkiewicz believes he could hit in the Majors right now. Stewart is also working on his versatility as the left fielder played three games in right for the first time in his career. -- KH
Kansas City Royals
It was feast or famine for hitters against Carlos Hernandez last month. Across three of his starts, the Royals' No. 12 prospect held opponents to two runs on six hits and four walks with 23 strikeouts in 17 innings. But in the other two outings, Hernandez yielded 11 runs on 12 hits and four walks with five strikeouts in seven frames. The 21-year-old began the season in extended spring training as he stretched out before joining Class A Lexington on May 6. The Royals are high on the 21-year-old's ceiling and live fastball, and many believe he could be a top prospect. It will just depend on which version shows up. -- KH
Minnesota Twins
On the first day of May, Alex Kirilloff kicked off a remarkable streak with Class A Cedar Rapids. The 2016 first-round pick collected an extra-base hit in 13 straight games, the longest such stretch in the Minor Leagues since at least 2005. As the hits kept coming, Kirilloff boosted his average from .254 on April 30 to .319 on May 31. The left-handed hitter also raised his on-base and slugging percentages about 100 points each, to .374 and .568, respectively, as he earned a spot in the Top-100 rankings. Not to mention, all of this is happening during his first season back from Tommy John surgery. Because he missed all of 2017 and he's only 20, the Twins are in no rush to move Kirilloff, but if he keeps hitting the way he is, they may not have a choice. -- KH
Video: Cedar Rapids' Kirilloff knocks his fifth homer
AL West
Houston Astros
Cristian Javier, who's generally been electric since debuting in the Dominican Summer League at 18 in 2015, led the system with 40 punchouts in May. Toeing the slab for the Class A Quad Cities River Bandits, the Astros' No. 14 prospect also posted a 1.96 ERA over five games -- three starts -- and walked seven over 23 innings compared to 12 in 16 April innings. Meanwhile, up at the Triple-A level, Rogelio Armenteros didn't allow more than three runs in any of five starts for Fresno, going 3-0 with a 2.70 ERA after suffering to a 5.12 mark in the opening month. Slugger J.J. Matijevic was promoted from the Midwest League to the Carolina League and quickly established himself with Buies Creek, which continues to have the best pitching staff in the circuit. -- Josh Jackson
Los Angeles Angels
For the last week and a half, Inland Empire's San Manuel Stadium has been the place to be for Angels fans who are also prospect hounds. The system's No. 1 guy, Jo Adell, arrived with the Class A Advanced 66ers from the Class A Burlington Bees on May 22, two days after the arrival of No. 4 Brandon Marsh. Jahmai Jones, No. 3 in the system, has been with Inland Empire all year. Although Adell had just seven hits over his first nine California League games, three of them were home runs, giving him eight dingers on the month. No Minor Leaguer hit as many as 10 homers from May 1-30, but Jared Walsh -- who was promoted from Inland Empire to Double-A Mobile on May 23 -- is among the eight players who had one more longball than Adell in that span. Walsh posted a .363/.471/.775 slash line over 23 games between the two levels, and his presence with the BayBears only makes Taylor Ward more of a danger in the Southern League. Ward, the Angels' No. 13 prospect, has batted .345 through 42 games this year, and over the last month he's hit four homers and stolen five bases. Griffin Canning also continued his work toward an incredible debut season. -- JJ
Oakland Athletics
While Jesus Luzardo demanded attention over the first month of the season, No. 12 A's prospect Logan Shore has separated himself in the second month. Like his left-handed counterpart, righty Shore started the year with Class A Advanced Stockton and earned a promotion to Double-A Midland. Unlike Luzardo, Shore was making up for lost time -- he spent the opening weeks of the season in extended spring camp following a right lat strain. First getting into action for the Ports on April 29, he coasted through four Cal League starts, fanning 25 over 22 1/3 innings while going 2-0 with a 1.21 ERA. His first two Texas League outings featured 10 punchouts over 11 2/3 innings, as he allowed five runs -- four earned -- for a 3.09 ERA. -- JJ
Seattle Mariners
The ongoing saga of top Seattle prospect Kyle Lewis began a promising chapter as the outfielder made his 2018 debut with Class A Advanced Modesto on May 12 and took about two weeks to put up a two-homer, four-RBI game. Through his first 15 games back in action after February arthroscopic surgery on his troublesome right knee, he's hit .279/.313/.475 while showcasing his skills in the outfield.
Evan White, the M's No. 2 prospect, has been decent for the Nuts, too, collecting 10 extra-base hits and 11 walks over 28 games. -- JJ
Texas Rangers
After a dominant April, Jonathan Hernández turned in a dazzling May, giving him the look early on of a breakout prospect. The 21-year-old righty and son of a former Major Leaguer leads the Carolina League with 73 strikeouts over 54 1/3 innings -- with 45 whiffs across 32 May innings -- and he's second on the circuit with a 1.66 ERA. The Rangers' No. 13 prospect had a 4.03 ERA over 23 games -- 22 starts -- between two levels last year. Sixth-ranked Texas prospect Bubba Thompson took platelet-rich plasma injections in his knees in the fall and was held in extended spring camp until May 9, but he's burst onto the South Atlantic League scene. The 19-year-old outfielder batted .279/.333/.492 with five doubles and five stolen bases over his first 15 games. -- JJ
NL East
Atlanta Braves
With top prospect Ronald Acuña Jr. on the verge of graduating from prospect status, pitcher Kolby Allard might have upped his stock more than anyone in the Atlanta system in May. Over five starts for the month, Allard went 3-0 with a 1.80 ERA and 1.09 WHIP. Atlanta's No. 6 prospect wasn't the only arm to shine. Ian Anderson -- the Braves' No. 5 -- struck out 34 batters in 28 innings and put up a 1.93 ERA. On the position player side, third baseman Austin Riley raked at a .293/.347/.457 rate and bashed four homers in May, driving in 18 runs. Outfielder Drew Waters was even better, posting an organization-best 1.054 OPS in his 20 May games thanks to a .325/.379/.675 slash line. -- Tyler Maun
Miami Marlins
Top prospect Monte Harrison's overall numbers dipped -- his average from .253 to .239 and OPS from .787 to .725 -- but his power bat is coming alive. After two homers in April, Harrison belted five in May. Miami's No. 21 prospect, Pablo López continued a dominant start to 2018. Making six of his eight starts so far this season last month, Lopez is the owner of a 0.62 ERA for the year, having allowed just three earned runs on 30 hits in 43 2/3 innings. The righty has struck out 51 batters against eight walks and limited opposing hitters to a .184 average. Righty Sandy Alcantara, an acquisition from the Marcell Ozuna trade now pitching in Triple-A at just 22, allowed three or fewer runs in four starts for the month. -- TM
New York Mets
Another month, and Peter Alonso is showing few signs of slowing down. The Mets' first base prospect matched his April homer total with seven blasts and improved his RBI total (25, six more than April) while OPSing .935 for the month. While seeing time exclusively in the outfield, Jhoan Urena batted .313/.361/.475 in 28 May games. He can also handle corner infield spots. Columbus lefty David Peterson dominated on the mound despite going 0-3. Peterson allowed just four earned runs in 32 1/3 May innings, striking out 32 batters and posting an organization-best 1.10 ERA and 0.89 WHIP for the month.-- TM
Philadelphia Phillies
The Sixto Sanchez Show continued for the Phils' top prospect in the season's first full month. Sanchez worked to a 2.38 ERA in four May outings, dropping his season-long ERA nearly a full run. In 22 2/3 innings for the month, Sanchez struck out 27 and walked just three. Two levels up, Enyel De Los Santos impressed at Triple-A. De Los Santos boasted a stingy 1.70 ERA through his first nine outings this season, five of which came in May. Though he pitched with traffic -- issuing 14 walks in 32 innings -- De Los Santos limited opposing hitters to a .144 average for the month. At the plate, Joey Meneses shined for Lehigh Valley. Meneses played in 29 games and batted 315/.350/.639, bashing nine home runs (and 16 total extra-base hits) in May. -- TM
Washington Nationals
Juan Soto's May was more impressive than almost any player in baseball. Soto started the month in Class A Advanced, jumped to Harrisburg on May 10 and finished the month in the big leagues. His former Potomac teammate Carter Kieboom put up eye-popping numbers in the Carolina League, batting .391/.458/.576 with three homers and 19 RBIs in 23 games for the month. A pair of P-Nats turned in dominant months on the mound. Sterling Sharp registered a 1.55 ERA in five starts for May, while rotation-mate Wil Crowe put up a 1.95 mark in five outings (four starts). -- TM
Video: Kieboom hammers a grand slam for Potomac
NL Central
Chicago Cubs
Trevor Clifton showed he can bounce back like the best of them. The 23-year-old started May by allowing two runs on two hits and three walks without completing the first inning. But then he turned right around and spun six one-hit frames in his next outing. If not for that first start, Clifton's ERA for the month would have been 1.73 in 26 frames as three of his last five starts were scoreless. The right-hander is repeating Double-A after an abysmal 2017 campaign with Tennessee, though he's playing just 30 miles away from where he grew up. As Clifton continues to shut down batters, he could be finally ready to head north to Iowa and maybe Chicago come September. -- KH
Cincinnati Reds
Playing just six games, it was a tough month for Nick Senzel. On May 3, the club's top prospect left the game after an at-bat in the first, and a few days later, he was put on the disabled list with vertigo, a condition he battled in September, too. After a couple weeks, he went to Arizona to get back in the groove and on May 29, he returned to Triple-A Louisville. Following a couple hitless games, the 22-year-old showed off his skill set with a two-run double, a walk and stolen base to close out the month. While vertigo can be a bewildering condition, the Reds hope Senzel can return to fine-tuning his swing and getting comfortable at second base. -- KH
Milwaukee Brewers
Keston Hiura's first full season got off to a slow start, but once the calendar changed to May, all that changed. The Brewers' top prospect hit .377 with six of his seven home runs and 23 RBIs. And once he got on base, Hiura kept going, swiping three of his four stolen bases and scoring 29 of his 38 runs. After cautiously beginning the season as a designated hitter, Hiura has played 15 games at second base in May without making an error. His stellar month on the field and at the plate earned the 21-year-old a promotion to Double-A to start June. But before the move was official, Hiura went 5-for-5 with two long balls in his final game with Class A Advanced Carolina. --KH
Pittsburgh Pirates
May 2018 was statistically the best month of Kevin Newman's career thus far. The 2015 first-round pick went from hitting .234/.253/.312 in April to .361/.410/.435 the following month. With the big boost, Newman put himself in the top five of the International League with 57 hits and 30 runs scored. The 24-year-old's big month was highlighted by an 11-game stretch where he went 24-for-49 (.490) with four extra-base hits and six RBIs. To top it off, Newman is hitting almost as well against righties as he is against lefties, leaving IL pitchers struggling to figure the leadoff hitter out. -- KH
St. Louis Cardinals
The Cards have made a lot of moves already this season, including calling up Alex Reyes, Jack Flaherty and Austin Gomber -- three of their top pitching prospects. With all that movement, it created a spot at Triple-A Memphis for Ryan Helsley. And so far, he's earned it. St. Louis' No. 4 prospect shook off a tough first start to May to throw four straight quality starts across Double-A Springfield and Memphis. Helsley notched a composite 2.16 ERA with 40 strikeouts and walks in 33 1/3 innings over the five outings. His .140 opponents' batting average for the month ranks third in the Minors. If the 23-year-old right-hander can keep it up, it won't be long before it's his named being called next. -- KH
NL West
Arizona Diamondbacks
Emilio Vargas, the D-backs' No. 30 prospect, leads the Cal League with a 1.41 ERA, thanks in large part to allowing a total of six runs -- four earned -- in the season's second month. He punched out 35 and walked nine across 27 2/3 innings over five May starts, and he's allowed one home run all season. Journeyman third baseman Juniel Querecuto hit the disabled list on May 31, but over his last 26 games for Double-A Jackson batted .359/.408/.489. That's actually a bit of a cool down from April, when he hit .392/.430/.486 over 20 games with the Generals. Renae Martinez, a 24-year-old non-ranked catcher, made mincemeat of Midwest League pitching over 19 May games, going 28-for-68 (.412) with eight walks, six doubles and four homers. -- JJ
Colorado Rockies
After a confusing first month in the big leagues, Ryan McMahon was sent to Triple-A Albuquerque on May 2 and posted a .320 on-base percentage with three homers, five doubles and a triple over 22 games. It earned him a trip back to the Majors on May 26, and he logged at least one hit in each of the first five games of his return, doubling three times. Meanwhile, in the Double-A Eastern League, top Colorado prospect Brendan Rodgers kept up the consistency he established in April but added power in the second month, bashing seven homers to go with six doubles and a triple over 28 games this month. -- JJ
Los Angeles Dodgers
Connor Joe, Double-A Tulsa's unranked third baseman, has been Minor League Baseball's toughest out in May, posting a .505 on-base percentage over 24 games through May 30. He also banged out 10 doubles in that span. Dean Kremer, another of LA's unranked, was third in the Minors with 46 strikeouts over six May starts, going 3-1 with a 3.03 ERA for Class A Advanced Rancho Cucamonga. DJ Peters' contact fell off a bit in the Texas League, but he did hit six May dingers. More noteworthy, though, MLB.com named him the No. 98 overall prospect, placing him on the Top 100 list for the first time. -- JJ
Video: Connor Joe jolts his sixth homer
San Diego Padres
Chris Paddack, out for a year and a half following Tommy John surgery, made his Class A Advanced debut on the last day of April and has been one of the Minors' best pitchers since. Over six starts, he's 3-1 with a 2.27 ERA and 51 strikeouts over 31 2/3 innings. He's part of a Lake Elsinore staff that may have the most potential of any in baseball. Franmil Reyes has been relatively quiet since his promotion to the Majors in the middle of the month, but he practically made his callup inevitable. Over the first 12 games of May with Triple-A El Paso, he went 23-for-41 (.561) with a whopping nine homers -- a tally that's gone unsurpassed for the month by any Minor Leaguer through May 30.-- JJ
San Francisco Giants
A groin strain shelved No. 2 San Francisco prospect Chris Shaw on May 16, which may not have been particularly devastating -- it's not a serious injury -- except that the hulking outfielder/first baseman was on pace for a historic month for Triple-A Sacramento. He went yard five times over 14 games, doubling seven times. Austin Slater. No. 5 in the system, has helped offset the River Cats' loss of Shaw, putting up five multi-hit games since May 17 and hitting .372 on the month. Top Giants prospect Heliot Ramos appears to be finding his footing after a rough start with Class A Augusta. From May 18-26, the 18-year-old outfielder went 10-for-26 (.385) over seven games. -- JJ
