Here's a look at the top pitching performers in each league for the week ending June 30:
Ethan Martin, Lehigh Valley
(2-0, 0.64 ERA, 2 G, 2 GS, 14 IP, 5 H, 1 R, 1 ER, 0 HR, 0 HBP, 8 BB, 10 K)
After a handful of rough outings early on, Martin has come on strong for the IronPigs, winning eight of his last nine decisions and each of his last four starts. Two of the wins came last week; following six strong innings at Columbus during which Martin allowed one run on three hits Tuesday, MLB.com's No. 71 prospect tossed eight scoreless two-hit frames against the Mud Hens on Sunday. Martin has held IL hitters to a .233 average, but ranks second on the circuit with 52 walks over 86 2/3 innings.
Pacific Coast League
Danny Duffy, Omaha
(2-0, 0.00 ERA, 2 G, 1 GS, 10 2/3 IP, 5 H, 0 R, 0 ER, 0 HR, 0 HBP, 3 BB, 11 K)
Duffy underwent Tommy John surgery for a torn ulnar collateral ligament on June 13, 2012, and returned to action for Double-A Northwest Arkansas on May 26, 2013. Joining Triple-A Omaha on June 10, the 24-year-old left-hander was hit hard in his first three starts, posting a 7.71 ERA. Last week he rebounded for his first post-surgery victories, tossing five scoreless frames at Oklahoma City Tuesday and 5 2/3 more against Iowa, fanning seven, on Sunday. Duffy threw 87 pitches Sunday and is recovering the form that saw him start the 2012 season in the Royals' rotation.
Eddie Gamboa, Bowie
(1-0, 0.00 ERA, 1 G, 1 GS, 1 CG, 1 SHO, 7 IP, 0 H, 0 R, 0 ER, 0 HR, 0 HBP, 3 BB, 5 K)
Heading into his fifth season with Double-A Bowie, Gamboa decided to try something different: a knuckleball. It's a pitch few have relied on and fewer have mastered, but it seems to be coming naturally to the 28-year-old Orioles farmhand. A week after taking a no-hitter into the eighth inning, Gamboa tossed a seven-inning no-hitter in the first game of Sunday's doubleheader for his first career shutout. Gamboa, who says he feels like a rookie again, is holding EL hitters to a .230 average -- 65 points lower than his rate last season.
Henderson Alvarez, Jacksonville
(0-0, 0.00 ERA, 1 G, 1 GS, 7 2/3 IP, 2 H, 0 R, 0 ER, 0 HR, 0 HBP, 0 BB, 7 K)
Alvarez made 31 starts in the Majors (for the Blue Jays) last season and is working his way back there (for the Marlins) in a rehab assignment that took him to Jacksonville last week. He showed no signs of rust on the mound or at the plate, pitching 7 2/3 scoreless frames and blasting a home run in his third pro at-bat. In two starts with the Suns, the 23-year-old Venezuelan has allowed five hits and no walks while fanning 13 over 14 1/3 shutout innings.
Brooks Pounders, NW Arkansas
(1-0, 0.00 ERA, 1 G, 1 GS, 1 CG, 1 SHO, 9 IP, 0 H, 0 R, 0 ER, 0 HR, 1 HBP, 0 BB, 6 K)
Pounders began the season in the Naturals bullpen and did not join the rotation full-time until May 13. He and his right arm are fully acclimated to making starts after pitching the first individual no-hitter in Northwest Arkansas history Thursday night, fanning six and hitting one batter in his first career complete game. He did not walk a batter. The 22-year-old needed 98 pitches -- 70 were strikes -- to turn the trick.
Daniel Winkler, Modesto
(2-0, 1.26 ERA, 2 G, 2 GS, 14 1/3 IP, 2 H, 2 R, 2 ER, 1 HR, 0 HBP, 4 BB, 15 K)
On June 15, Winkler took a no-hitter into the seventh inning. Nine days later, the 23-year-old right-hander combined with two relievers for Modesto's first no-no since 1987. Winkler has demonstrated a rare dominance of the hitter-friendly Cal League: he leads the circuit in ERA (2.02), innings (98), wins (11), strikeouts (113, also most in the Minors) and WHIP (0.76). A 20th-round pick in 2011, Winkler has allowed just 49 hits in 98 innings for a .147 average against.
Luke Jackson, Myrtle Beach
(1-0, 0.00 ERA, 1 G, 1 GS, 7 IP, 2 H, 0 R, 0 ER, 0 HR, 0 HBP, 2 BB, 6 K)
A first-round pick in 2010, Jackson won his fourth consecutive start Thursday night, tossing seven scoreless innings, to earn his league-leading eighth victory. The Rangers' No. 11 prospect also leads the circuit with a 2.30 ERA over his 14 starts; last year he posted a 4.39 mark in 13 outings during the second half of the 2012 campaign. Jackson particularly loves pitching in Myrtle Beach, where he sometimes surfs between starts -- he's 5-0 with a 0.79 ERA in seven starts at TicketReturn.com Field.
Florida State League
Brent Suter, Brevard County
(1-0, 1.00 ERA, 1 G, 1 GS, 1 CG, 9 IP, 5 H, 1 R, 1 ER, 1 HR, 0 HBP, 1 BB, 5 K)
A Harvard product with a good hockey name, Suter has proven a steal as the Brewers' 31st-round pick in 2012. The left-hander won his third straight outing Friday, allowing one run on five hits over nine innings in his first career complete game. Suter ranks fourth in the FSL with a 1.09 WHIP and sixth with a 2.87 ERA after going 4-1 with a 2.23 mark in five June outings.
Scott Griggs, Great Lakes
(1-0, 0.00 ERA, 3 G, 7 IP, 1 H, 0 R, 0 ER, 0 HR, 0 HBP, 3 BB, 15 K)
It can be tough to stand out as a reliever, but striking out 15 batters while allowing one hit over eight innings is a solid recipe for being noticed. That's what the 22-year-old Griggs did for the Whitecaps last week, dropping his ERA to 2.29 in 27 relief appearances. In 35 1/3 innings this season, Griggs has allowed 17 hits (for a .139 average against) and struck out 57. He's also issued 26 walks, but his lack of command has not hurt him lately: he hasn't given up a run in 11 appearances dating back to May 26.
South Atlantic League
Luis Diaz, Greenville
(2-0, 0.69 ERA, 2 G, 2 GS, 13 IP, 6 H, 1 R, 1 ER, 0 HR, 0 HBP, 3 BB, 15 K)
Diaz was roughed up last season, his first in the Sally League, posting a 3-8 record and 6.01 ERA in 20 outings (17 starts). The 21-year-old's second go-around has been far more successful, culminating in back-to-back wins last week -- including seven one-hit frames at Kannapolis on Sunday that saw him fan a season-high nine batters. After allowing batters to hit .315 off him last year, Diaz has held them to a .206 mark in his last three outings for the Drive.
New York-Penn League
Aaron Griffin, Hudson Valley
(0-0, 0.00 ERA, 2 G, 1 GS, 8 IP, 4 H, 0 R, 0 ER, 0 HR, 0 HBP, 0 BB, 6 K)
A 10th-round pick out of Loyola Marymount last month, Griffin was ripped for three runs in just 1 2/3 innings in his pro debut June 18. In his last two games -- both against Brooklyn -- however, he's looked more like his brother A.J., who pitches for the Oakland A's. The younger Griffin tossed four scoreless frames apiece in the two outings, allowing four hits and fanning six without issuing a walk. The 22-year-old righty has yet to issue a free pass as a pro and is holding NYPL hitters to a .208 average.
Chris Johnson, Salem-Keizer
(1-0, 0.00 ERA, 2 G, 2 GS, 12 IP, 8 H, 0 R, 0 ER, 0 HR, 1 HBP, 0 BB, 13 K)
Johnson notched just two wins, along with a 6.84 ERA in 16 outings -- six of them starts -- with the Volcanoes last season. He's already matched that win total and bettered his ERA by nearly six runs to 1.13 in his return to the Northwest League, this time working exclusively as a starter. Johnson turned in a pair of scoreless six-inning outings last week, giving up three hits to Vancouver on Monday and five to Hillsboro on Saturday. He fanned 13 and did not walk a batter over the 12 frames.
Appalachian League (for period of June 20-30)
Edwin Diaz, Pulaski
(1-0, 0.00 ERA, 3 G, 3 GS, 16 IP, 9 H, 1 R, 0 ER, 0 HR, 0 HBP, 2 BB, 20 K)
The 19-year-old Diaz, a third-round pick out of Puerto Rico in 2012, has been all but perfect in his first three starts of the season, surrendering an unearned run on nine hits and two walks while racking up 20 strikeouts over 16 innings. Diaz has held right-handed batters to a .143 average and has dramatically improved his command since last summer, when he walked 17 batters over 19 innings for the AZL Mariners.
Pioneer League (for period of June 20-30)
Devin Burke, Grand Junction
(2-0, 1.64 ERA, 2 G, 1 GS, 11 IP, 7 H, 2 R, 2 ER, 1 HR, 1 HBP, 1 BB, 11 K)
After two pro starts, Burke has quieted whatever reservations left him undrafted out of Virginia Tech last month. The 22-year-old right-hander is a perfect 2-0 after pitching five scoreless one-hit frames against Orem on Friday night and has 11 strikeouts against one walk in his first 11 innings as a pro. The Owlz, victims in both of Burke's outings, managed seven hits off him for a .179 average.
John Parker is a contributor to MLB.com.