The Mets’ trainers’ room has been standing room only for most of the season, and pitcher Joey Lucchesi became the latest player assigned to the injured list, between games of Saturday’s doubleheader split in Washington.

Lucchesi, who tossed 5 ¹/₃ scoreless innings in a loss to the Nationals on Friday night, was shelved due to left elbow inflammation to clear roster space for the activation of outfielder Albert Almora Jr.

“He has some inflammation and he wouldn’t be able to make his next outing, going through his routine and everything he needs to do to get there,” Rojas said after the Mets lost 6-2 in Game 2 (they won 5-1 in Game 1). “The plan now is to get the inflammation down, that’s the focus.”

The left-hander has allowed just three earned runs in 22 ²/₃ innings over his past five outings, lowering his ERA for the season from 9.19 to 4.46. Lucchesi hasn’t yet been sent for an MRI exam “but will [be] at some point,” Rojas said.

Starting pitchers Carlos Carrasco (hamstring) and Noah Syndergaard (elbow) have been on the injured list all season, while staff ace Jacob deGrom has departed each of his past two starts early with right flexor tendinitis and shoulder soreness, respectively.

DeGrom, the two-time Cy Young winner, said following a side session Saturday that he plans to make his next scheduled start, in another doubleheader Monday against the Braves, as long as he doesn’t experience any soreness Sunday.

Rojas mentioned righty Jerad Eickhoff, who was with the Mets in Washington as part of their taxi squad. as a potential rotation fill-in for Lucchesi.

“We have some moving parts, we have a four-man rotation all of a sudden, but we do have some depth,” Rojas said.

Jeff McNeil will be activated from the injured list for Monday’s doubleheader against the Braves at Citi Field, Rojas confirmed. McNeil might serve as the designated hitter for Triple-A Syracuse again Sunday before he returns, the manager added.

Almora started in center field in Game 2, and rapped two doubles in three at-bats in his first appearance since suffering shoulder and toe injuries crashing into the wall May 11 against the Orioles. … The Mets acquired 24-year-old Double-A righty Troy Miller from the Blue Jays for Jacob Barnes, who was designated for assignment last week.

— Additional reporting by Mike Puma in Washington