Seranthony Domínguez’s slider isn’t moving the way it’s supposed to. Here’s how he’s trying to fix that.

SAN DIEGO — There was a time when Phillies reliever Seranthony Domínguez had one of the nastiest sliders in baseball. In 2022, it was a pitch that induced whiffs 57.1% of the time. This year, it has not been nearly as consistent. Domínguez isn’t getting as much swing-and-miss on it, and has already allowed three home runs on his slider alone.

It hasn’t had the same horizontal movement. So, Domínguez has begun to make some adjustments. None of them is mechanical, as of now, but he is experimenting with a few grips that could work better with his arm slot, and give him more movement.

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“He’s trying a couple,” said pitching coach Caleb Cotham. “It’s been a really good pitch. But hitters are knocking on the door — ‘Hey, maybe an adjustment is needed.’ And he’s willing to do that. I still feel really confident about it.”

Domínguez hasn’t settled on one grip yet, but has been trying a few over the past few weeks. He could end up using a curveball grip to throw his slider, or move his fingers up or down the horseshoe-shaped seams of the baseball. Cotham said Domínguez isn’t searching just to search. He is trying to be deliberate with his work.

“Really, all roads are leading to a more consistent shape that he can pitch with,” Cotham said. “Maybe a little more glove-side movement, or a little more depth. Just something to get off the barrel. I don’t want to take anything away from the hitter, but I think a lot of pitching coaches have said that a lot of home runs are thrown, not hit.

“So, if you have a pitch that you can throw down the middle, that still wants to get to the location you want — rather than having to start the ball at the location, because it doesn’t move quite as much — now you can play with the tunnel. On Friday night, he kind of did it. He can throw the slider down the middle, and it lands down and away. He can throw the four-seam down the middle, it lands away. He can throw the two-seam down the middle, it lands in.

“So you have a three-pitch … with lefties, you mix a changeup in there. It’s four different looks from the same spot. Same arm slot and same tunnel.”

These first few weeks have been frustrating for Domínguez. Going into Sunday’s game, he had an 8.68 ERA in 11 appearances. Hitters are barreling the ball 13.8% of the time against him, which is a career high. He’s throwing the ball hard but isn’t commanding it as well as he should. His slider not having as much bite is tied to many of these early-season struggles.

“A lot of times I throw it well, but it doesn’t have the movement I want it to have,” Domínguez said. “So I’m trying to work on the consistency of the slider.”

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Nevertheless, he has seen some positive signs. Domínguez and Cotham were encouraged by his outing on Friday in San Diego. He entered in the ninth inning with a 9-3 lead, and pitched a 1-2-3 inning with one strikeout. His slider was hard and late-breaking and moving the way it was supposed to.

They know not to get too ahead of themselves, but they think it was a good first step.

“From the bullpen to the game, it was more consistent,” Domínguez said. “The movement was there, which is what I’m looking for.”

Taijuan Walker was reinstated to the active roster on Sunday morning. To make room on the 26-man roster, righthander Ricardo Pinto was designated for assignment.

After Sunday’s game, manager Rob Thomson said that Cristopher Sánchez will start Monday in Los Angeles, Spencer Turnbull will start Tuesday, and Zack Wheeler will start Wednesday. When asked if Turnbull, who had been filling in for Walker, would move to the bullpen after this turn through the rotation, Thomson said he didn’t know.

Thomson said he wanted to give Wheeler and Nola some extra rest. It is still unlikely the Phillies go to a six-man rotation this early in the season.

“I don’t think we’d go to a six-man because we’ve got an off-day the following Thursday, so you end up giving guys too much time off,” Thomson said.