Not a Rookie: Marc Rzepczynski
Here's a look at Blue Jays lefty Marc Rzepczynski, one of the more successful rookie pitchers in baseball last year.
Rzep (I'm not typing that name again) was drafted by the Toronto Blue Jays in the fifth round in 2007, out of the University of California-Riverside. He was considered a second or third round talent before the college season, but his stock dropped slightly after he missed several weeks of pitching time with a sore elbow and a broken knuckle. He pitched very well in college (2.72 ERA, 84/25 K/BB with zero homers allowed in 73 innings), and continued to pitch very well after signing, posting a 2.76 ERA with a 49/17 K/BB in 46 innings in the New York-Penn League. Scouting reports indicated an 88-92 MPH sinking fastball, a good curveball, and a workable slider and changeup, giving him a four-pitch arsenal. I gave him a Grade C+ in the 2008 book, writing that he was a big sleeper heading into the season and using the "Sleeper Alert!" tag on his comment.
He missed April 2008 recovering from a fractured bone in his pitching hand, but took the mound in May and was very impressive for Lansing in the Midwest League, posting a 2.83 ERA with a 124/42 K/BB in 121 innings, allowing 100 hits and just two homers. He posted a 3.00 GO/AO ratio to go with the low homer rate. He showed tremendous polish for the Midwest League, but at age 22/23 he was a bit old for the level. I gave him a positive review in the '09 book, renewing the Grade C+ rating but noting that the Double-A transition would be critical for him.
Rzep began '09 with Double-A New Hampshire and transitioned well, going 7-5, 2.93 with an 88/36 K/BB in 77 innings with just one homer and a 2.58 GO/AO. Promoted to Triple-A, he pitched well in two starts (16/4 K/BB, one run in 11.1 innings) and was rewarded with a promotion to the majors. For the Blue Jays, he went 2-4, 3.67 in 11 starts, with a 60/30 K/BB ratio in 61 innings, allowing 51 hits with a 4.14 FIP. His GO/AO was 1.84. The Jays shut him down on September 1st to avoid overworking his arm.
Obviously this was very good rookie performance, and given his minor league track record I don't think it was a fluke. Sabermetrically, all indicators have always been positive for Rzep, and his components deteriorated by a very normal amount in the majors. The main thing he needs to do numberwise is lower his walk rate.
Scouting-wise, his fangraphs data indicates a fastball ranging between 86 and 91 MPH, averaging 88. He used his two-seam and four-seam fastballs 55% of the time, mixing in a slider 37% of the time, but making more limited use of his changeup (6%) and curveball (just 2%). Fangraphs rates his slider as his most effective pitch. He used the curveball and changeup more often in the minors than in the majors, and I'd like to see him mix in those pitches more frequently as he moves forward. I don't see any huge red flags in his delivery, which looks pretty smooth to me, although that's no guarantee that he won't get hurt of course. The Blue Jays did the right thing shutting him down in September in my opinion.
Rzep doesn't have the pure stuff to project as an ace, but if he can sharpen his command a bit more, I think he can be a good number four starter for a long time to come. His debut was impressive and I think he's still an underrated pitcher who will have a better career than many guys who get more publicity.