In-season farm system grades: AL, NL Central

With about six weeks left in the Minor League regular season, members of the MiLB.com staff hand out grades to all 30 farm systems based on their prospect and team performance so far. The American and National League East Division made up the first installment in the series, followed by the Central Divisions today and the West on Friday. Kelsie Heneghan provides the grades here for the AL Central, while Alex Kraft breaks out his red pen for the NL Central.

American League Central

Chicago White Sox
Grade: A-
It was a very exciting offseason for the South Siders as their system was bolstered by the additions of Yoán Moncada, Michael Kopech, Lucas Giolito and Reynaldo López. Chicago has carried that prospect-acquisition mentality into this season, picking up an impressive haul from the Cubs and Yankees -- most notably Eloy Jiménez, Dylan Cease and Blake Rutherford. While it's great to have an organization full of exciting names, many of its top prospects struggled in the first half. Kopech, Giolito, Lopez and Carson Fulmer have all had trouble keeping runs off the board, though they continue to rack up strikeouts. Beyond their current top 10, the deep White Sox also boast Alec Hansen, Jordan Stephens and Dane Dunning -- each of whom are enjoying dominant seasons on the mound. If they keep it up, those righties could gain their fair share of the spotlight, too. At the plate, top overall prospect Moncada reached Chicago this week after a solid first season at Triple-A. Just like the parent club, however, the Minor League squads are struggling in the win-loss columns. The system as a whole ranks 30th overall with a .426 winning percentage as Class A Kannapolis (49-45) is the only club with a winning record. There's too much talent to earn anything other than an A, but team performance is a factor in this evaluation -- hence the minus.

Cleveland Indians
Grade: B
While they're still the "Windians" in the Majors, overall the organization ranks 19th in winning percentage at .491 -- though the system still boasts three teams with records above .500. The best of those teams is Class A Advanced Lynchburg, led by Triston McKenzie. The system's top pitching prospect shuts down hitters at a thrilling rate with an above-average arsenal. One level up, top prospect Francisco Mejía is among the best hitters in the Minors, while Yu-Cheng Chang is bringing the power for Double-A Akron. Former top prospect Bradley Zimmer officially graduated to the Majors after starting the season at Triple-A Columbus and is playing a big role in the Cleveland outfield. Two-time first-round pick Brady Aiken continues to try to find his stride on the mound, though July is proving to be his best month yet. Cleveland's 2016 first-rounder, Will Benson, is also having a tough time finding his groove at the plate in his non-complex debut. Left-handers Shawn Morimando and Ryan Merritt remain solid options to be recalled, though the rest of the Triple-A Columbus rotation has been so-so. Overall, Indians fans have a lot to be excited about, but there are still a few key players who need time to figure things out.

Detroit Tigers
Grade: B-
For the Tigers, it's all about young arms and loud bats. After beginning the season in extended spring training, top overall prospect Matt Manning has been unstoppable on the mound for Class A Short Season Connecticut. Righties Beau Burrows and Kyle Funkhouser have shown that a midseason promotion can't slow them down as they climb the system. Burrows joined Tyler Alexander at Double-A, where the left-hander is struggling for the first time in his career. Outfielder Christin Stewart continues to be the system's most powerful bat, while Mike Gerber and Derek Hill have battled the injury bug. Led by Class A West Michigan's .692 winning percentage, the Tigers organization claims a .510 mark, which places them 10th in baseball. While reliever Joe Jiménez and outfielder JaCoby Jones have gotten tastes of the Majors, the system is fairly young overall, and it's tough to find a big name who hasn't taken a positive step in his development. The system still isn't going to be named in the same breath as, say, the Braves, White Sox or Yankees, but it's certainly trending upward.

Kansas City Royals
Grade: C-
Working their way into playoff contention, the Royals appear primed to make another run with most of their top prospects at the top two levels. (They've already gotten help this year from right-handers Eric Skoglund, Jake Junis and Miguel Almonte.) Versatile Ryan O'Hearn and Hunter Dozier could get their MLB calls this September, though the latter is currently recovering from a wrist fracture. Battling injury for most of the past three seasons, 2012 first-round pick Kyle Zimmer is finally getting innings again, now as a reliever. While all these guys appear to be on the right track, few are putting up the stats to show much progress. This is especially true for Josh Staumont, the organization's top pitching prospect, whose 70-grade fastball has translated to a lot of strikeouts, but also too many runs and walks. In terms of team performance, the organization's .490 winning percentage ranks 20th in the Minors. The system gets the most help from the middle of the ladder, with Double-A Northwest Arkansas, Class A Advanced Wilmington and Class A Lexington being the only squads above .500.

Minnesota Twins
Grade: B
Twins teams know how to win, that's for sure. The organization ranks second overall with a .592 winning percentage as all seven Minor League teams sport winning records. Top prospect Nick Gordon is heating up at the plate with Double-A Chattanooga, while teammate and No. 2 prospect Stephen Gonsalves has been missing bats all season. Fernando Romero, Kohl Stewart and Felix Jorge -- who are all in the team's top-10 prospect rankings -- round out a formidable Lookouts rotation. Twins prospects don't seem to have much problem on the field, but a few key players are having trouble staying there. After making his pro debut last year, 2016 first-round pick Alex Kirilloff underwent Tommy John surgery in May and will miss all of 2017. Tyler Jay returned from bicep tendinitis only to pitch two innings in May before suffering a shoulder injury, and the 2015 first-rounder has not pitched since. After missing two years from Tommy John, J.T. Chargois worked his way to the Majors last year, but two games into the 2017 season, he injured his elbow again. And the list continues with hard-throwing righty Nick Burdi, whose season is done due to elbow surgery. While those major injuries hurt the system, the winning attitude and talented players who are on the field give the Twins plenty of promise.

National League Central

Chicago Cubs
Grade: C+
The Cubs system received a shake-up with the loss of top prospects Eloy Jiménez and Dylan Cease in a trade for White Sox starter Jose Quintana. Both enjoyed solid first halves with Class A Advanced Myrtle Beach and Class A South Bend, respectively, and deserve recognition for helping the North Siders acquire a quality, controllable starting pitcher. As in past years, Chicago has done a stellar job of graduating players to the big leagues and turning them into contributors. Ian Happ represents the biggest example, while corner infielder Jeimer Candelario, outfielder Mark Zagunis and catcher Victor Caratini have also gotten their shots. Cubs affiliates as a whole have been successful with only Triple-A Iowa and the Arizona League squad sitting below .500. However, the Quintana trade stripped the system of much of its star power. While they have some interesting players in the lower Minors, there's a dearth of Major League-ready pitching talent in the system, which may have motivated them to execute the Quintana trade in the first place. It's a system that's trending down, but we have to give some credit for all that it's accomplished thus far in 2017.

Cincinnati Reds
Grade: B-
Nick Senzel, the second overall pick of last year's Draft, has come as advertised. The 22-year-old third baseman owns a .305/.372/.465 slash line in 85 games between Class A Advanced Daytona and Double-A Pensacola. Jesse Winker has continued his usual steady production with Triple-A Louisville, while right-hander Tyler Mahle emerged as a force in Pensacola's rotation before heading to the Bats. Class A Dayton has an impressive collection of young talent as well with outfielder Taylor Trammell, catcher Tyler Stephenson, outfielder T.J. Friedl and right-hander Tony Santillan. On the flip side, Cincinnati checks in at 21 among the 30 organizations in combined winning percentage. Louisville, in particular, has struggled, sitting in the basement of the International League West. Individually, there's a lot to like in the Reds system. Collectively, in terms of team performance, not so much. 

Milwaukee Brewers
Grade: A-
One of baseball's deeper systems has lived up to the hype in the first half, with impact contributors up and down the ladder. Triple-A Colorado Springs has led the charge, boasting a star-studded lineup with the likes of top prospect Lewis Brinson, outfielder Ryan Cordell and a resurgent Brett Phillips. A number of players from the team made their big league debuts, including highly touted lefty Josh Hader, who's carved out a role in Milwaukee's bullpen. Corbin Burnes, the Brewers' 2016 fourth-round pick, has been one of the Minors' best-kept secrets. The righty was arguably baseball's best pitcher in the first half, going 7-1 with a Minor League-best 1.09 ERA, 2.19 FIP and 22 walks against 104 strikeouts in 107 1/3 innings between Class A Advanced Carolina and Double-A Biloxi. All that talent has not necessarily translated into wins, however. Other than Colorado Springs (59-35), the majority of their full-season affiliates are close to or below .500. It's not a major issue, as the Minor Leagues are primarily about development, but it's enough to keep them from attaining a perfect score.

Pittsburgh Pirates
Grade: C+
There are certainly some things to like about the Pirates system as it stands. Triple-A Indianapolis and Double-A Altoona sit atop their respective divisions, while Class A Advanced Bradenton also checks in with a winning record. Individually, recent first-round picks Cole Tucker (2014) and Will Craig (2016) have raked in the Florida State League, with the former ranking second in the Minors with 34 stolen bases, and 25-year-old lefty Steven Brault sits atop the International League with a 2.00 ERA. The issue for the Pirates comes from the top of their prospect charts. Austin Meadows (No. 1) got off to a sluggish start with Indianapolis before going down with a right hamstring strain in late June, while fellow top-100 prospects Mitch Keller and Kevin Newman have had ups and downs of their own this season. Newman is at least tracking up and earned a promotion to Indianapolis this week, while Keller continues to find himself following his return from a back strain. With a general lack of depth, especially when it comes to Major League-ready talent, Pittsburgh will need more from its stars in the second half.

St. Louis Cardinals
Grade: B
Per usual, the Cardinals have had a very successful Minor League campaign. To this point, the club's affiliates have produced the fifth-best winning percentage among all 30 teams, and Class A Advanced Palm Beach has already wrapped up a Florida State League playoff spot. Among the individual standouts, catcher Carson Kelly, outfielder Harrison Bader, infielder Paul DeJong and righty Luke Weaver have Triple-A Memphis atop the Pacific Coast League American Southern Division. Some, such as Weaver and DeJong, have also contributed in the big leagues. Right-hander and 2014 first-round pick Jack Flaherty dominated at Double-A Springfield, joined the Redbirds by early June and is an easy top-100 candidate again. Dominican outfielder Magneuris Sierra showed plenty of speed in the Florida State and Texas Leagues and finds himself as an outfield asset in St. Louis for the third time this season. Obviously, the injury to No. 9 overall prospect Alex Reyes hurts, and it's what keeps the Cards from a higher grade. The righty possesses electric stuff, and a strong campaign from him could've elevated the Cardinals among some of the top systems in the game. Another promising righty, Sandy Alcantara, has struggled with the jump to Double-A.