Not to beat a dead horse – OK, maybe to beat a dead horse – but MLB has been moving into a post-steroid era of great pitching, and a look at 2011’s rookie class suggests that trend is only going to continue. While there are some impressive young hitters and position players making waves this season, the most dominant first-year performances have all been on the mound.

Here’s a look at baseball’s five best rookies after two months.

5. J.P. Arencibia, C, Toronto Blue Jays

Arencibia has delivered exactly what the Jays expected from their young catcher. He’s tied for third amongst all catchers in baseball with eight home runs – despite splitting time with Jose Molina – and looks like he’ll be one of the best power bats in Toronto’s line-up for years to come. His catching and game-calling have both gradually improved, and he has only recently taken over catching for the entire staff, so his offensive numbers are only going to improve.

The Jays have hung around the MLB standings in the AL East, and if Arencibia can keep improving at, and behind, the plate, they might just have a Wild Card run in them.

4. Mark Trumbo, 1B, Los Angeles Angels

The silver lining to Kendry Morales’s ankle injury last May – which will now sideline him for all of 2011 – has been the emergence of Trumbo as his replacement. The big slugger leads all rookies with 10 home runs (“Trumbombs” as MLB Network host Ahmed Fareed calls them), and only veteran Torii Hunter has driven in more scores for the Angels. He’s flashed the ability to steal a base on occasion, and will only improve as he continues to adjust his swing.

3. Zach Britton, SP, Baltimore Orioles

The 23-year-old left-hander has been the biggest bright spot for the plucky Orioles, who are surprisingly still in the hunt in the murderous AL East. He’s been pitching like a seasoned vet, posting 8 quality starts in 11 appearances with a WHIP of 1.22 and an ERA of 2.93, both outstanding for a first-year player. He’s not striking out a lot of hitters – just 4.84 K’s per nine innings – and opposing line-ups have been catching up with him in his last two starts, but it looks like Britton might be the anchor the O’s can build their staff around.

2. Jeremy Hellickson, SP, Tampa Bay Rays

Unlike Britton, Hellickson has only got performed better as the season has progressed. He’s quickly become the third-best arm in the Rays’ dangerous rotation, tormenting smart hitters with what is already one of the best changeups in baseball. The only guy who has had much success hitting it is Jose Bautista, but he’s been hitting everything. If the Rays continue their steady play since an ugly start, expect Hellickson to be right near the top of the AL Rookie of the Year conversation.

1. Michael Pineda, SP, Seattle Mariners

But he probably won’t pass Pineda. The hard-throwing 22-year-old might be the best starter on the Mariners, and the guy pitching ahead of him in the rotation is reigning Cy Young winner Felix Hernandez. Seattle’s offence has been a disaster once again this season, but thanks to the 1-2 combo of King Felix and Pineda, they’re right in the thick of the AL West race.