Toledo – Thad Weber (RHP)
On the heels of a fantastic start to the season, right-hander Thad Weber earned his first trip to the big leagues. Working as both a starter and reliever for the Mud Hens in April, Weber posted a nifty 0.64 ERA and 2-0 record in 14 innings across three appearances. In those 14 innings, Weber allowed a miniscule six hits and two walks while fanning 16 International League hitters. His .128 batting average against was yet another indicator of his early-season dominance, making him one of Toledo's top arms at the start of the season.
Runner-Up: Chris Bootcheck (RHP)
Erie – James Avery (RHP)
Coming up on his 28th birthday, right-handed starter James Avery may be removed from serious prospect status, but that doesn't mean he's not making some noise in the Eastern League. In four starts last month, Avery posted a 3-1 record and 2.42 ERA while spinning 22 1/3 innings. He allowed only 19 hits, though three of them were long balls, finishing with an average against of .229 for the month. His 2:1 strikeout-to-walk ratio is further evidence of his strong start and standing as Erie's early-season ace.
Runner-Up: Ryan Robowski (LHP)
Lakeland – Tyler Clark (RHP)
Clark may be an unheralded reliever drafted in the 24th round in 2010, but he has turned in an outstanding start to the season out of the Lakeland bullpen. In five appearances, four of which spanned more than one inning, Clark tossed 8 2/3 innings of stellar relief. He has allowed six hits and just three walks while whiffing eight batters and posting a 2.08 ERA. In the early going he has been an invaluable bridge from the starters to the late inning relievers like closer Bruce Rondon who is this month's runner-up.
Runner-Up: Bruce Rondon (RHP)
West Michigan – Michael Torrealba (RHP)
Torrealba ventured back to the Midwest League after a 2.22 ERA in 43 games in 2011, picking up right where he left off last year. He appeared in nine games in April without allowing a run and picked up three saves. Across 11 2/3 innings, Torrealba yielded only three hits and five walks while striking out 13 hitters. His opponents average of .081 is nearly unheard of and has some fans calling for his promotion to High-A Lakeland to test his skills in the late innings.
Runner-Up: Tommy Collier (RHP)