SAN DIEGO -- The Detroit Tigers' Jordan Zimmermann has got a handle on his pitching. He'll get to prove it again against the San Diego Padres in Sunday's series finale.

"Since he re-found that grip it has coincided with his turnaround," Detroit manager Brad Ausmus said.

Zimmermann had what was considered a gray May. He lost three of his four decisions that month and entered June wondering if the gloom would persist.

Instead, he produced four straight quality starts. Over that stretch, Zimmermann had a 1-1 record with a 2.70 ERA and 21 strikeouts in 26 2/3 innings.

"He re-found his old slider grip and that has been the main difference," Ausmus said.

Before finding it and going on his four-start run, Zimmermann was scuffling. He had surrendered at least four earned runs in seven of his 10 starts with a 6.47 ERA.

Then Zimmermann discovered what was lost. The bite in his slider was back and soon, so was Zimmermann.

"The slider went from being flat to having depth," Ausmus said. "It became more of a swing-and-miss pitch, a groundball pitch. That was probably the main reason and it made his other pitches more effective as well."

Ausmus said Zimmermann's obstacle isn't seen on a regular basis.

"It doesn't happen often," Ausmus said. "Usually it's a gradual thing, like you just slowly start to move (your grip) and you don't even notice it until the break is different.

"It could happen over an offseason. You pick up a ball and you just don't pick it up the right way. It has been just a thoughtless thing to do for years and then in spring training you pick it up differently and you don't even recognize it."

Zimmermann is 3-2 with a 1.69 ERA in eight career starts versus the Padres. He hasn't allowed a run in his last two starts against San Diego and enters with a 15-inning scoreless streak.

He was with the Washington Nationals when last facing the Padres in 2015 and made himself right at home at Petco Park. Zimmermann got the win when firing six innings of scoreless ball, allowing six hits and a walk.

In five career starts at Petco, Zimmermann is 3-1 with a 0.50 ERA and 40 strikeouts in 36 innings.

The Padres will counter with Clayton Richard (5-7, 4.20 ERA), the lone southpaw in their rotation. Richard has shined of late, producing four quality starts in his last six times out. He's gone 3-2 with a 3.32 ERA during that span.

Richard is making his third start against the Tigers and his fifth appearance overall. He's won his only decision against Detroit.

San Diego goes for the three-game sweep because in part of Hector Sanchez's second pinch-hit homer of the season.

The Padres have missed Sanchez's bat since he went on the disabled list in May for a foot contusion.

"We haven't had any left-handed power on the bench," Green said. "And no left-handed pinch-hitters."