The already thin Mets bullpen got even thinner Friday. 

Top high-leverage reliever Dedniel Nunez was placed on the 15-day injured list with a right pronator teres (forearm) strain and struggling long man Adrian Houser was designated for assignment to make room for Kodai Senga, who made his regular-season debut, but then suffered a left calf strain during the Mets’ 8-4 victory over the Braves. 

Losing Nunez is a significant blow for a bullpen with few trustworthy arms, even if manager Carlos Mendoza believes it will be a short stay for the young reliever.

Nunez, who has pitched to a 2.43 ERA with a 0.93 WHIP in 33 ¹/₃ innings this year, felt stiffness in his right forearm after each of his last two outings and underwent imaging.

Tests showed no structural damage in his elbow. 

“Obviously, we put him on the IL, but we got good news there,” Mendoza said. “The ligament, the elbow, everything is fine. This should be a short stint.” 

The Mets recalled right-hander Eric Orze for bullpen depth.

The initial plan was to go to a six-man rotation, which meant one less reliever, a major factor in the decision to DFA Houser.

But then Senga was injured Friday, and now the Mets will shift back to a five-man rotation. 

Shintaro Fujinami, signed in the offseason to a one-year, $3.35 million deal, was also designated for assignment.

It was either that or put him on the 40-man roster since his time on the 60-day injured list with a right shoulder strain was up.

Fujinami had been pitching for Triple-A Syracuse. 

The next few days, at least, will be difficult for the bullpen.

Senga exited early with a calf strain — he had yet to appear in a game this season because of injury — and Tylor Megill has pitched into the sixth inning in just two of eight major league starts this year. 

Jose Butto, a revelation as a reliever, is likely unavailable until Sunday after throwing 40 pitches in Thursday’s win.

Phil Maton had appeared in three of the past four games, as well, before Friday. Inconsistent veterans Adam Ottavino and Jake Diekman could see expanded roles, with each throwing an inning in Friday’s win.

It’s uncertain when newcomer Ryne Stanek, acquired in a trade with the Mariners, will arrive and be activated. It hasn’t helped that Mets starting pitchers haven’t been going deep into games. 

There is hope the bullpen will be fortified in the long run.

Sean Reid-Foley and Reed Garrett are working their way back from injuries.

Nunez isn’t expected to be out long.

And general manager David Stearns is expected to make relief additions.

But for now, the unit is in a tough spot. 

“I keep saying guys will step up. Guys will get opportunities. Pretty confident that they will,” Mendoza said. “We’ve talked about our depth. Guys continue to come through those doors from Triple-A, from the outside. We’ll give them the ball and they’ll step up. We’ve got guys here who’ve done it before, and they’ll continue to do it.”