Two Aces Cannot Pitch Every Inning of 54 Games
Eduardo Rodriguez is 14-4 with a 2.50 ERA. Brandon Pfaadt is 7-1 with a 3.29 ERA. Those two lines represent genuine, rare pitching quality — the kind of foundation that wins divisions in healthy years. They are also, at this moment, the entirety of Arizona's functional rotation. And that is not a foundation. That is a tightrope.
The number that matters most right now isn't either ace's ERA. It's 5.6 — runs allowed per game over Arizona's last ten contests, up from a prior baseline of 4.1. A spike of 1.5 runs per game doesn't sound catastrophic until you do the arithmetic across 54 remaining games. At that rate, the Diamondbacks are surrendering roughly two additional runs per week beyond what their season-long pitching had been giving up. Over a stretch run where every game carries playoff weight, that gap between what this staff was and what it has become is the difference between a wild card berth and a quiet October.
The reason for the collapse isn't mysterious. Twelve pitchers are currently on the injured list. Michael Soroka, who had been a legitimate third option at 8-5 with a 3.84 ERA before his shoulder gave out on August 23, is gone. Zac Gallen and Ryne Nelson were already on 60-day assignments. Corbin Burnes never came back. What's left behind Rodriguez and Pfaadt is Merrill Kelly, who is 8-13 with a 5.68 ERA — a back-of-rotation arm being asked to carry starter innings in a pennant race. That is not a rotation. That is two aces and a structural problem.
I've been tracking this staff's deterioration all month, and the piece I wrote on August 23 made the case that both sides of the ledger were bleeding simultaneously. That remains true. The offense is averaging 3.6 runs per game over the last ten, down sharply from the season's earlier pace. But the offensive shortfall at least has a plausible near-term remedy: Ketel Marte is expected back, and Jordan Lawlar is day-to-day. The pitching depth has no equivalent cavalry coming. The arms on 60-day assignments aren't returning in time to matter.
What makes this genuinely dangerous for Arizona's playoff chances — they sit two games behind the last wild card with 54 to play — is the compounding math. Rodriguez and Pfaadt cannot start every game. On the days they don't pitch, this staff is being asked to hold opponents to fewer than four runs with a collection of arms that has been allowing 5.6. The 5-5 record over the last ten games flatters the situation; a negative run differential in a stretch where you split evenly means you're winning the games you shouldn't lose and losing the ones you need to win. That's not a formula for closing a two-game gap. That's a formula for treading water until the season ends.
My read is this: Arizona's playoff window does not close because of the offense. It closes, if it closes, because two elite starters cannot manufacture innings for an entire roster's worth of missing arms. Rodriguez and Pfaadt are doing everything asked of them. The question is how long the structure around them can hold before the 5.6 stops being a recent spike and becomes the permanent number.