SAN FRANCISCO — Blake Snell felt he was close to turning a corner after enduring a rough start to his Giants career, but the reigning National League Cy Young winner won’t get a chance to right the ship for a while.

Snell was scratched from his scheduled start against the Mets on Wednesday after landing on the 15-day injured list with a left adductor strain, retroactive to April 23. Snell, who suffered the inner thigh injury during his most recent bullpen session, has dealt with the same issue twice before and said he’s hoping he won’t miss much time beyond the requisite 15 days.

“Obviously, disappointed,” Snell said following the Giants’ 8-2 defeat at Oracle Park. “I felt really good this week throwing, even during the bullpen. I was like, ‘Man, I feel really good.’ The ball was coming out good. I made some adjustments that I think are going to be big for me. Just swing-and-miss on a couple of the pitches I was throwing that weren’t getting that.

“Overall, I was pretty excited about what I was going to be able to do today if I pitched. Having that [injury] was pretty upsetting. Now I’ve got to change my focus to get back healthy and get back to pitching.”

Snell’s injury forced the Giants to stage a bullpen game in their series finale against New York, with right-hander Ryan Walker serving as an opener for the first time this year.

Walker worked a scoreless inning in his 14th career starting assignment, but his fellow relievers couldn’t hold the line, as Sean Hjelle, Landen Roupp and Mitch White combined to give up eight runs over five innings, denying the Giants their first three-game sweep of the year.

The Giants fell to 0-5 when Snell’s turn in the rotation has come up this year. Opponents have outscored them by a 55-12 margin on those days, two of which were spot starts from Walker and Daulton Jefferies.

“As we sit here right now, it hasn’t been our best day,” manager Bob Melvin said. “But hopefully [Snell] comes off the IL and pitches better than he has before. It was a tough spring for him, really no spring. April’s not his best month to begin with. Nothing we can do about it now except try to patch it up and pitch better on that turn.”

Snell joined the Giants as a free agent on a two-year, $62 million deal (with an opt-out after 2024) on March 19. Because he signed so close to Opening Day, Snell didn’t get to appear in a Cactus League game during Spring Training, which prevented him from facing true big league competition until he debuted with the Giants on April 8.

The unorthodox ramp-up seemed to hamper Snell’s performance on the mound, as the 31-year-old left-hander ended up going 0-3 with an 11.57 ERA and a 1.97 WHIP in 11 2/3 innings over his first three starts of 2024.

Snell believed he made progress after giving up five runs over 4 2/3 innings in his last start against the D-backs on Friday, but he shut himself down after tweaking his adductor, which also sidelined him for a month in 2021 and for three weeks in ‘22. Snell said he feels stronger now and will be aiming to beat those timetables in the coming weeks.

“My arm feels good,” Snell said. “My body feels good. The groin is the only thing that’s going to get there. I’m a lot more confident about how I feel right now. In ‘21, I knew it was going to be a while. In ‘22, I was more optimistic. I feel even better about this one. I caught it early.”

The Giants will have off-days on Thursday and Monday, so they could hold off on filling Snell’s spot in the rotation until May 4 at Philadelphia if they wanted to. Still, Melvin said the Giants also want to try to get an extra day of rest for their other starters, most notably Logan Webb, who tossed a season-high eight innings on Tuesday night.

Snell’s injury could ultimately open the door for pitching prospect Mason Black to get his first look in San Francisco’s rotation. Black, the Giants’ No. 7 prospect, has logged a 1.53 ERA with 20 strikeouts over 17 2/3 innings in his first four starts of the year for Triple-A Sacramento. The 24-year-old right-hander isn’t on the 40-man roster, so the Giants would have to create a spot to add him to their rotation mix.

“It seems like every time, he gives us five innings and does well,” Melvin said. “[Black] would definitely be one of the options, but I’m not sure where we’re going with that.”