PHOENIX — Arizona Diamondbacks southpaw Andrew Saalfrank has stymied hitters since returning to the mound this season in part by, in the words of pitching coach Brian Kaplan, being weird.

A 6-foot-3 lefty with a three-quarter arm slot who does not throw hard and drops a curveball off the table is not a common sightline for hitters.

He still has to execute, and he has.

The Diamondbacks entered a phase of their season after the trade deadline when auditions for younger players became more prevalent.

Blaze Alexander has captured headlines for stepping up among position players, and Saalfrank has been the standout in the bullpen.

“He’s a unique slot, really unique pitch shapes, the velocity probably a little bit lighter than what they expect at the back of the game,” Kaplan told Arizona Sports. “It’s just hard for guys to plan for or feel like they’ve seen it before. So it just sneaks up on them and he’s got this killer mentality, just goes after guys and attacks the zone and doesn’t care what the radar gun says. He just feels confident in his stuff.”

Saalfrank has worked a 1.11 ERA in 24.1 innings since his return from a yearlong gambling suspension, giving up runs in two of 23 outings.

Among pitchers with at least 20 innings pitched, he ranks second in Major League Baseball in ERA. Only Boston closer Aroldis Chapman is lower at 0.98. Saalfrank’s 0.90 WHIP ranks 14th.

What has made Saalfrank successful has been his effectiveness against both lefties and righties.

Lefties are hitting .182 (4-for-22) against him and slugging .227, while righties are batting .188 (12-for-64) and slugging .250. The Diamondbacks have four lefties in the bullpen, so having someone capable of overcoming typical platoon splits has been beneficial.

Another factor — his 6.5% walk rate is the lowest he’s produced at any level since he was drafted and below the league average of 8.4%. That had been a flaw of his game in the past (10.5% in Triple-A last year, 13% in MiLB in 2023). His command in the strike zone has improved, so while does not pile up strikeouts, he’s been able to draw grounders and lazy fly balls.

“I think execution-wise for me has been really good this year,” Saaalfrank told Arizona Sports. “Just trying to get ahead and stay ahead. … For me specifically, adding that four-seam, like the little four-seam cutter thing, whatever you wanna call it, has made the other two pitches for me a lot better.

“I get more like respect, I think, in the zone now the hitters don’t necessarily have to look just bottom half. So that’s opened up my game a little bit just in terms of like being able to pitch … versus like flip a coin sinker or curveball, which one is it?”

Andrew Saalfrank’s new pitch paying off early

When Saalfrank broke out in September 2023, he was exclusively a sinker-curveball pitcher, and this year, he has thrown a new fastball 15% of the time.

He described the grip as a four-seamer that he tries to cut.

The idea is that the pitch has extra carry on it than the sinker, allowing him to attack the upper part of the strike zone and keep hitters guessing more.

The 28-year-old does not even average 90 mph with it, but opponents are only hitting .067 against the pitch so far.

His velocity is still not where it had been before his suspension, from which he was activated in early June. His sinker averaged 92.4 mph in 2023, and it now sits at 89.2 mph.

That’s a reason manager Torey Lovullo believes Saalfrank has more in the tank and will continue to evolve as he builds up.

“Andrew’s very dependable,” Lovullo said. “He missed an entire year of baseball and I think the stuff is gonna get better. I think the fastball velo continues to tick up. It’s a big swing-and-miss breaking ball. He’s doing a fantastic job, and I think he’s got more in him.”

The Diamondbacks have had to use Saalfrank and just about everyone else in the bullpen in different situations due to a lack of defined roles at this point.

The sample size is still smallish, but so far he has held up.

His season has been a success story as someone who prepared himself to jump back into the fire quickly once the suspension was lifted. In just over a month after he was allowed back at Salt River Fields, he returned and has been a key cog, auditioning well for roles in the bullpen moving forward.