Marc Rzepczynski in 2010
Let’s take a look at Marc Rzepczynski, the second year starter that is essentially guaranteed a spot in the rotation due to his 2009 season & Cito’s early spring comments;
Short Statistical History
The southpaw is a strikeout and groundball machine. He’s averaged about a K per inning throughout his pro career. In the minors he forced groundball rates as high as 65% and during his short 2009 big league stint he induced 51.5% GB. He throws 60% fastballs (88ish), 30% sliders (80ish) and mixes in a change to round things out. His final 2009 line include 3.67 ERA, 3.70 xFIP and a 2/1 K/BB ratio.
What drives Marc’s success? His super nasty slider.
According to Fangraphs pitch value run estimators Marc has one of the best sliders in the majors. His slider ranked as the second best pitch on the entire Jays staff in 2009, behind only Jason Frasor’s fastball.
Shifting through pitch F/X data showcased just how dominate Marc’s slider really is.
| Total | |
| Sliders | 426 |
| Balls | 147 |
| Called Strikes | 97 |
| Swinging Strikes | 52 |
| Foul Balls | 72 |
| HBP | 1 |
| In Play Outs | 44 |
| Singles | 8 |
| Doubles | 2 |
| Triples | 1 |
| Home Run | 1 |
| Errors | 1 |
Awesome. Look at all of the called strikes. Hitters are obviously fooled by the slider. In-fact opponents overall percentage of swings at pitches in the strike zone (Z-Swing) is 53% vs Marc, which is over 15% percentage points lower than league average. Even Doc’s Z-Swing rate was 66%.
Moving on, here are the total outcomes via the slider (balls in play, hits, walks, strikeouts, etc)
| Outcome | Total |
| Total Outs | 76 |
| Balls in Play Outs | 44 |
| Strikeouts | 32 |
| Hits | 12 |
| Walks | 10 |
| HBP | 1 |
Using these numbers here is the standard BA/OBP/SLG line of the slider
| BA | OBP | SLG |
| 0.136 | 0.232 | 0.216 |
Dominating, plain and simple. To put this number into perspective NL pitchers hit a combined .140 in 2008.
Marcel predicts a 4-5 season with a 4.05 ERA in 2010. After seeing these slider numbers I’m putting Marc down for a minimum of 10 wins, a strong K-rate and an above average xFIP.
I’ve liked Rzepczynski from the start, for a seemingly inexplicable reason. I guess the reason is not so inexplicable anymore. It will be very interesting to see what he can do this year.
I like Rzep a lot too. I think the reason people are so hesitant to jump on the bandwagon, along with Litsch, and even Romero and Marcum to some extent is that their stuff isn’t “sexy”. It never piqued the scouts’ interest and nothing really jumps out at first glance. Then you look at the numbers and you realize they’re damn good. Jays fans have come to expect JP’s draft picks to max out at simply “solid” because they weren’t highly-ranked prospect, but Rzep, Marcum, and Romero are all very good #2/3 starters on any team and I don’t think they are one-trick ponies. Marcum and Romero especially seem to have great makeup, perhaps from watching Doc, to go along with their changeups. Hopefully Rzep learned something too. Long way of saying: prospect rankings aren’t gospel.