Consistency has not exactly been Brandon Pfaadt's strongest quality in his four years of pitching for the Arizona Diamondbacks. Both his raw ERA numbers and his underlying predictive metrics have fluctuated to a high degree during his young career.

But 2026 was a very firm step toward true reliability for the 28-year-old right-hander.

And with so many questions about the state of the Diamondbacks' rotation moving forward, how Pfaadt performs in 2027 could be one of the X-factors in Arizona's quest for a return to the playoffs.

Brandon Pfaadt's 2026 season was massive positive step

Pfaadt's season was not unlike that of Ryne Nelson's back in 2025.

Due to a rotational logjam — and three poor starts to begin the regular season — Pfaadt was moved to the Diamondbacks' bullpen in early April. That did not work; he was knocked around for a 5.91 ERA over the course of 21.1 relief innings.

And so, Arizona sent him down to Triple-A to work on some things. He was quickly recalled to the majors and re-inserted into the rotation after Nelson suffered an unexpected elbow injury.

With some small tweaks made in Triple-A, Pfaadt excelled from that point on.

In 98 innings as a starting pitcher post-recall, Pfaadt pitched to a 2.94 ERA, a 3.36 expected ERA and a 3.29 FIP. That added up to a 3.77 full-year ERA, despite a 5.92 at the time of his option.

Opposing batters hit .239 off him and he struck out under six batters per nine innings in that span, but he also walked just 3.8% of batters and allowed an average exit velocity of 88 MPH, which would be about a tick better than average for a full season.

He also allowed only seven home runs in that stretch, with a full-year HR/9 of 0.93. That was his best full-season figure by a wide margin, considering the long ball has been a regular problem for him.

The most impressive part was simply how extended and consistent his success became. And that's why 2027 is such an important year for the righty.

Why 2027 is massive test for Brandon Pfaadt

In 2023, Pfaadt's debut season, he struggled as a rookie. His ERA fell about 30 points shy of 6.00. After an unexpectedly-dominant postseason, he looked poised to take over a bigger role in the rotation in 2024.

2024 looked like it was trending that direction. Pfaadt begun to stack quality performances until they totaled a 3.92 ERA at July's end. But a brutal month of August and September ballooned it back to 4.71 by 2025's conclusion — despite his peripherals all in the mid-3.00s.

There was hope he'd bounce back in 2025, but he struggled to another 5.00-plus ERA season last year.

2026 is the first time Pfaadt has extended his positive contributions into a lengthy stretch of dominance. His shift away from a strikeout-focused approach fell in line with Arizona's overall pitching output, and it led to more sustainable success.

But now, Pfaadt is an important cog in a concerningly depth-lacking rotation. Eduardo Rodriguez's ace-like 2026 season could regress. Nelson is a question mark due to health and underperformance in 2026. Merrill Kelly struggled in 2026 and Corbin Burnes looked brutal in his three post-injury appearances.

Kohl Drake, Mitch Bratt and Jose Cabrera all struggled in their debut seasons. There aren't many arms in the system worthy of stepping into a major league role if needed.

With so many questions about next season's rotational stability and consistency, Pfaadt has a chance to prove his success can continue for more than a partial season. Arizona's rotation may very well depend on it.