Seranthony Domínguez stood on a bullpen mound and mimicked his delivery without throwing a ball. It was a few hours before the Phillies played Thursday night, and Domínguez was searching for something.

“Physically I feel good right now,” he said later while sitting at his locker. “My arm’s good. Velocity’s good. But something’s wrong.”

The results say as much. Domínguez has made four appearances since returning from a 3½-week absence due to triceps tendinitis. The first two were easy, breezy — six batters up, six down. The last two were train wrecks — eight runs on five hits, including two home runs, four walks, 13 batters faced, three outs recorded.

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Domínguez’s arm strength seems to be sound. His sinker averaged 98.5 mph Wednesday night, including a 99.3 sizzler that Toronto’s Vladimir Guerrero Jr. hit for a three-run homer in the eighth inning.

The Phillies believe the issues stem from a small mechanical flaw. As Domínguez explained it, his arm may be “a little late” in relation to the rest of his body, affecting his command. Only 25 of his last 53 pitches have been strikes. Maybe it’ll be an easy fix.

But there’s also no ignoring the fact that Domínguez has thrown 47 innings, mostly in high-leverage situations, after scarcely pitching the last two seasons while recovering from Tommy John elbow surgery. Might he simply be hitting a wall?

“It could be that,” interim manager Rob Thomson said. “It could be the fact that he has had [four] outings since he’s been back, so he might be just a little bit rusty. But it’s command. It’s being able to throw a slider in the right spot.”

Thomson said the Phillies likely will begin using Zach Eflin in late-inning situations to alleviate the load on Domínguez and David Robertson, specifically. A starter throughout his career, Eflin came back this month after missing two months with right knee pain.

“I’m not afraid to use him in any situation,” said Thomson, who believes Eflin may adapt well enough to being a reliever to eventually pitch on back-to-back days. “The state of the game doesn’t bother him. That’s what really gives me confidence.”

Regardless, the Phillies need their relief ace to bounce back before the end of the season. Even after the last two outings, Domínguez has a 2.87 ERA and a 30.3% strikeout rate.

“It’s tough,” Domínguez said. “The team needs me right now. I’m just working on some mechanical things and trying to figure it out.”

Hall pass

In a pregame ceremony, the Phillies presented first baseman Darick Hall and right-hander Andrew Painter with the Paul Owens Award, given annually to the organization’s top minor league player and pitcher.

Hall couldn’t attend because he was playing at triple A, which raised the question: Why is Hall still playing in triple A?

During Bryce Harper’s two-month absence with a broken thumb, Hall hit nine homers and slugged .550. But he hasn’t been called back up in September, even though the roster expanded to 28 players, because the Phillies want him to keep getting regular at-bats. Donny Sands, who got called up instead, hasn’t had a plate appearance since Sept. 3.

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“It’s just a matter of, where’s he going to play, where’s he going to get at-bats, other than pinch-hit at-bats?” Thomson said of Hall. “I’d rather see Darick get consistent at-bats in case somebody goes down, then we can just put him right in.”

Thomson didn’t rule out putting Hall on the postseason roster as a left-handed pinch-hitter, especially because the triple-A season will be over by then.

Hall had 27 homers and a .546 slugging percentage in 414 plate appearances in triple A through Wednesday.

Extra bases

Braves star Ronald Acuña Jr. was scratched with back tightness. ... After throwing 58 pitches Wednesday night in his return to the rotation after a monthlong absence, Zack Wheeler will have his pitch count increased by about 15 to 20 pitches for his next start, scheduled for Tuesday night in Chicago. ... The Phillies honored area scout Zach Friedman with the annual Dallas Green Award and low-A Clearwater manager Marty Malloy with the John Vukovich Award. ... Aaron Nola (9-12, 3.38 ERA) will start Friday night against Braves right-hander Jake Odorizzi (5-5, 4.04).