The highest-profile addition to the Phillies’ revamped bullpen landed on the injured list Sunday.

Archie Bradley will miss at least 10 days with a strained oblique muscle in his left side, the Phillies announced before the finale of their three-game series in Atlanta. The right-hander said he’s not sure how the injury occurred nor how long it will keep him sidelined.

“It’s not something I can pinpoint,” Bradley said. “It wasn’t one particular act that I felt it on. It’s going to be at least 10 days, and then from there we’re just waiting, trying to get more answers on the severity.”

Left-hander JoJo Romero was recalled from the Lehigh Valley alternate site to take Bradley’s seat, if not his specific role, in the bullpen. Manager Joe Girardi has used Bradley in the seventh and eighth innings.

Bradley faced three batters, allowed two hits, and was charged with the deciding run in Saturday night’s 5-4 loss in Atlanta. He has given up two runs on four hits and one walk while recording three strikeouts in three innings over four appearances.

“When I got done [Saturday], obviously I wasn’t very happy with the results, kind of sitting there I was like, ‘Man, I can really feel this in my side. I’m going to say something.’ I don’t know. We just kind of discussed that it was probably the best choice for me to go on the IL.”

The Phillies’ bullpen, a train wreck of historical proportions last year, has been a source of strength so far. The six primary relievers -- Héctor Neris, José Alvarado, Bradley, Connor Brogdon, Brandon Kintzler, and Sam Coonrod -- combined to allow four runs in 22 innings through eight games.

» READ MORE: Phillies' new-look bullpen all about high velocity and ‘creating an attitude’

For his part, Bradley said the results could be better.

“I’m not pumping 97, 98 like I want to, but I’ve found a way to get it done and pitch,” said Bradley, whose average fastball velocity has declined gradually each season since 2018 and is at 93.2 mph thus far this year. “I would love to see my [stuff] bounce back up to 95-97. Maybe this gives me a chance to reevaluate some things.”

Romero was one of the Phillies’ final roster cuts in spring training, a move that was made primarily because he could be optioned to the minors without exposure to waivers. But the Phillies also wanted him to get ahead in the count more consistently.

Girardi said the Phillies received positive reports on Romero from the staff in Lehigh Valley, for whatever it’s worth. The alternate-site team has been playing exhibition games against their counterparts from the New York Mets and New York Yankees.

“I don’t think you can make too much always of what’s going on down there,” Girardi said. “Because there’s a different heartbeat and it’s a different world up here. I think we’ll know better if he gets in a game.”

Romero began his major-league career with six strikeouts in 3 2/3 scoreless innings in his first four appearances last season. After a few rough outings near the end of the season, he finished with a 7.59 ERA in 12 appearances.

The Phillies have not had good injury luck in recent years after signing free-agent relievers, with Tommy Hunter, Pat Neshek, and David Robertson all missing time. Bradley has been on the injured list only twice previously in six major-league seasons, both times in 2015 with a right sinus fracture and right shoulder tendinitis.

About Saturday night

A defensive breakdown cost the Phillies on Saturday night, when Alvarado fielded a ball to the left of the mound, turned to second base to start a potential double play, and saw nobody covering. Instead of getting out of the inning, the Phillies allowed the go-ahead run to score from third base.

Girardi found fault with neither Alvarado’s instinct to throw to second nor shortstop Didi Gregorius’s inclination to try to field the ball rather than being in position to cover the bag. After watching the play again, Girardi figured the Phillies simply had a lapse in communication.

“If you’re from Didi’s perspective behind the pitcher, it was going to be to the right of Alvarado, so Didi went for the ball,” Girardi said. “The communication has to take place where Didi’s yelling, ‘4! 4! 4! Home! Home! Home!’ The catcher’s got to see that, too, and that’s probably where the breakdown was.”

» READ MORE: Phillies option reliever JoJo Romero to minor-league camp, leaving one lefty in bullpen

Extra bases

With left-hander Drew Smyly starting Sunday night for the Braves, the Phillies bumped lefty-hitting Gregorius down one spot to seventh in the order. A .248/.300/.374 career hitter against lefties (compared to .271/.320/.455 against righties), Gregorius was 1-for-10 with six strikeouts against lefties through eight games. He hit a three-run homer against Smyly in the fourth inning. ... Chase Anderson is scheduled to start Monday night in the opener of a four-game series in New York. The Mets will counter with lefty David Peterson, who gave up six runs in four innings against the Phillies last Wednesday at Citizens Bank Park.