After waiting more than half the season for Kodai Senga’s return from the right shoulder strain that had sidelined him since spring training, the Mets may now be without the right-hander for the remainder of the regular season with a left calf strain suffered in his return to the mound Friday. 

Carlos Mendoza delivered the news of the “high grade” strain before Saturday’s 4-0 loss to the Braves, with the manager leaving open the door of a potential return for Senga in the postseason, should the Mets make it that far.

“It’s hard to put a timetable on it, but I think it’s pretty fair to say he’s pretty much done for the regular season,’’ Mendoza said. “It’s a huge blow, but we got to this point without him. It sucks for him, for all of us. The way I see it, we’ve been through a lot and we got to this point. If we get to see him pitch again this year, it means we’re in a good spot. Hopefully, that’s the case.”

And even an October run by the Mets doesn’t guarantee Senga getting back on a mound at all this year.

“Especially with the calf, it’s tricky,’’ Mendoza said. “We’re looking at eight to 10 weeks before he’s a big-league pitcher, [able to throw] 85 pitches. It’s hard to predict when you’re dealing with this.”

The extended absence of Senga, who was placed on the 15-day injured list Saturday, will make the Mets’ road to the playoffs more difficult.

Senga suffered the injury when he raced off the mound after an Austin Riley pop-up and fell to the ground Friday night at Citi Field.

It came after he pitched 5 ¹/₃ solid innings in his season debut that was expected to be the beginning of a strong second-half push for Senga, who emerged as the team’s ace a year ago.

“It sucks,” Mendoza said of Senga’s new injury.

Tylor Megill, already scheduled to start Saturday against the Braves at Citi Field, was recalled from Triple-A Syracuse to take Senga’s spot on the roster and will now remain in the rotation for the foreseeable future. 

The Mets were already looking for bullpen help prior to Tuesday’s trade deadline and must decide whether to add another starter from outside the organization.

And the injury could cost Senga his chance of opting out of his five-year, $75 million deal following next season.

He needed to pitch 400 total innings from 2023-25 in order for the opt-out to kick in, so Senga may remain a Met through the 2027 season, since he’s tossed just 171 ²/₃ innings since the beginning of last year.

Senga’s injury comes on the heels of Christian Scott also landing on the 15-day IL with a strained UCL that has him shut down for two weeks.

If his elbow doesn’t respond to the rest, Scott could be gone for all of this year — or longer if he needs Tommy John surgery.

“I still feel good with our options and depth,’’ Mendoza said. “Guys will step up. We’ve got five legitimate starters here. They put us in the position we’re in now.”

But David Stearns’ job in his first deadline in Queens as the team’s president of baseball operations just got harder.

And the plans of moving to a six-man rotation, as had been the case when Senga returned, are now on hold.

“As I sit here, we’ll stick to a five-man [rotation], especially because of off days,’’ Mendoza said.

But their rotation and depth will be tested more than it has all season in the coming weeks, particularly after Thursday’s off day.