PHILADELPHIA — Orion Kerkering flexed his arms as he strutted off the mound and toward the first-base dugout, rewarding Phillies manager Rob Thomson’s confidence in the young right-hander.

With a pair of Cardinals runners on second and third with one out in the top of the eighth inning on Wednesday afternoon, Thomson took out his best reliever, lefty-hander José Alvarado, in favor of Kerkering to protect a one-run lead. The 24-year-old flamethrower responded with two crucial outs against the righty batters in the middle of the St. Louis order.

This year has been shaky at times for Kerkering, but he was lights-out in that spot. He got Nolan Arenado to pop out to first base on a sweeper, then froze Willson Contreras with a full-count sinker for a called third strike. He continued his recent stretch of success to escape the jam and help the Phillies take a 2-1 win in the first game of a doubleheader at Citizens Bank Park.

“That’s three outings in a row that he’s been pretty good,” Thomson said, “and each outing he’s gotten a little bit better. At that point, we needed to shut it down right there. And I just liked the right-on-right matchup better.”

After posting a 5.56 ERA in 13 appearances in March and April, Kerkering has turned it around in May. He’s allowed one run in 5 1/3 innings during his six games this month, and he’s kept opponents scoreless for three appearances in a row. On Wednesday morning, Thomson said he liked the way Kerkering has “attacked” lately, and he certainly went after the two hitters he faced during the game.

Kerkering fell behind the veteran Arenado 2-0, but he bounced back with a well-placed sweeper on the outside corner to induce a pop-up into foul territory. In a battle with Contreras with first base open, the reliever challenged him with a 97 mph sinker on the outside corner for strike three. Kerkering was excited to secure the hold and set up Jordan Romano for the save in the ninth.

“He’s got some of the best stuff in the league,” Romano said. “Kerk coming in, in that spot today, seeing him get those two big outs, it kind of pumps up the boys. When I see him get that last strikeout, it kind of pumps me up.”

Romano, inked to a one-year deal in Philadelphia, also struggled to begin the season and has shown signs that he’s rounding into form. He sat down the Cardinals with three strikeouts to close out the victory in his sixth consecutive scoreless appearance. Despite the 8.22 season ERA, he’s pitching with conviction and leaning on his breaking ball.

“The slider is really good right now, and he’s landing it,” Thomson said. “It’s almost like a short curveball. It’s really late, really deep. He’s got a lot of confidence right now.”

Kerkering and Romano were expected to be the two go-to right-handed arms out of the Phillies bullpen entering the year, and they have been this month. They’ve both been reliable as they’ve distanced themselves from some of the early blow-ups.

Philadelphia’s relief unit looked a bit thin coming into the season with a lot riding on its four best relievers: Alvarado, Romano, Kerkering and Matt Strahm. The Phillies’ 4.64 bullpen ERA currently ranks 23rd in the major leagues, but that number could come down if Kerkering and Romano keep producing when the team hands them the ball in key situations.

The Phillies lost the second game of their doubleheader, 14-7, after a career-worst night by starter Aaron Nola; the bullpen did not fare much better, either. But in Game 1, with their best relievers ready to go, the Phillies found a winning blueprint with Kerkering and Romano filling their roles to perfection.

“I feel like we’re just trying to keep that going,” Romano said, “just having good innings, give it to the next guy and do that.”