Blake Snell (3-2, 1.97) vs. Zac Gallen (9-13, 5.13).
Zac Gallen has been one of Arizona's stalwarts since joining the Diamondbacks in 2019, his rookie year: 61-47 record with a 3.62 career ERA. That has not been the case for Gallen this year, but at least he has made 27 starts this year, which is 21 more than Blake Snell.
That said, Snell has a 2025 WAR of 0.6, while Gallen's is 0.5. So there you have it. I suppose you can take more than half the season off and still contribute a bit.
The Padres are playing the cream-puff Twins this weekend, so we'd better win this series.