How Will the Top Rookie Pitchers From Last Season Perform in 2015?
Dellin Betances, New York Yankees
By both fWAR, rWAR, and WARP, no reliever, rookie or veteran, was more valuable than Betances. The 6'8" righty was tops in fWAR (3.2) and WARP (2.6), and tied with Wade Davis for the lead in rWAR (3.7).
He led all relievers in innings pitched with 90, posting a 1.40 ERA (or an ERA- of 36), 43 FIP- and 50 xFIP-. He was fourth among all relievers with a 39.6% strikeout rate (13.5 per nine) and had a 7.0% walk rate (2.4 per nine).
The projections, particularly PECOTA and Steamer, are bearish, but that is to be expected, as projection models tend not to be great at projecting starters converted to relievers. Betances struggled as a starter in the minor leagues, so the systems are factoring in 641 innings of a 3.99 ERA pitcher. The dominant relief ace we saw last year is a different pitcher than that, so use caution with these projections.
| Player | IP | ERA | K/9 | BB/9 | WAR/WARP |
|---|---|---|---|---|---|
| numberFire | 70.1 | 2.56 | 10.7 | 3.1 | X |
| Steamer | 65 | 2.85 | 11.7 | 3.66 | 1 |
| ZiPS | 82.2 | 2.39 | 12.6 | 3.6 | 1.5 |
| PECOTA | 55 | 3.93 | 10.3 | 4.6 | 0.3 |
Again, Betances’ strike profile is probably instructive here. His swinging strike rate of 21.2% would have been tied for second in the American League, behind only Tanaka, if he had faced enough batters to qualify. Also, his 32.2% looking strike rate would have tied for fifth in the league. As mentioned, as Podhorzer writes, swinging and looking strike rates are the most predictive of future strikeouts among the strike variations, while foul strike rate correlates with strikeouts less and is more random.
