Preview: 4/5 @ Cardinals

This is Robbie Ray’s fourth season in Arizona, and he has now made 40+ starts both at Chase Field and elsewhere. While the W-L marks have been almost the same, the underlying numbers have not been equitable:

• Home: 14-16, 4.92 ERA, 217.2 IP, 231 H, 128 R, 119 ER, 32 HR, 95 BB, 261 K
• Road: 15-16, 3.01 ERA, 251.1 IP, 198 H, 97 R, 84 ER, 27 HR, 99 BB, 302 K

His ERA at Chase is almost two runs higher than elsewhere - and his last outing, where he was tagged for seven runs (albeit still getting the win) against the Rockies, appears to suggest the problem hasn’t been solved with the introduction of the humidor. Among all pitchers for Arizona with 100 or more innings pitched both at home and away, Ray’s split is the second-largest. Here are the top 10 by ERA difference (a positive figure is better at home; a negative one, better on the road):

1. David Hernandez: 1.99 (home 2.68 vs. road 4.67)
2. Robbie Ray: -1.91 (4.92 vs. 3.01)
3. Jose Valverde: -1.50 (4.01 vs. 2.51)
4. Elmer Dessens: 1.49 (4.26 vs. 5.75)
5. Greg Swindell: -1.41 (4.49 vs. 3.08)
6. Claudio Vargas: -1.35 (5.47 vs. 4.12)
7. Trevor Cahill: -1.30 (4.98 vs. 3.68)
8. Edgar Gonzalez: 1.28 (5.39 vs. 6.67)
9. Patrick Corbin: 1.27 (3.47 vs. 4.74)
10. Randall Delgado: 1.24 (3.55 vs. 4.79)

Overall, for their entire history, the Diamondbacks have pitched slightly worse in their own park, but the difference is only -0.17 (4.32 vs. 4.15), so Ray’s ERA gap is more than eleven times as much. What’s the cause? His strikeout rate is identical, 10.8 both in Chase and other parks. He does a better job of keeping the ball in the park elsewhere, with a road HR rate of 0.97 compared to 1.32 at home. But a big difference is the batting average for balls in play. On the road, Ray is an economical .289. But in Phoenix, that spikes by 60 points, to a rough .349. Part of that could be park factors: but the overall team BABIP figure is just two points higher (.301 vs. .299). I’m open to suggestions why Ray’s is SO much more extreme.