The struggling Edwin Diaz was placed on the 15-day IL Wednesday with a right shoulder impingement, another blow to an already reeling bullpen.

And it at least partially explains Diaz’s recent lack of performance, as he was yanked from the closer role and continued to pitch poorly.

Over his previous five appearances, Diaz has blown three saves, giving up 10 hits, three walks and eight earned runs over 4 ⅓ innings.

He last pitched Saturday, when he blew yet another save in a loss to the Giants.

The 30-year-old missed all of last season after suffering a torn patellar tendon in his knee during the World Baseball Classic.

His return to the bullpen was expected to provide a boost to a unit that was undermanned a year ago, but after a strong first month of the season, Diaz has been subpar.

The right-hander said following his most recent rough outing that he felt good and on Tuesday, David Stearns, president of baseball operations, spoke optimistically of Diaz’s future.

“I think Edwin’s a really good pitcher, an elite-level pitcher, who’s going through a rough patch,” Stearns said. “And I expect him to come out of it and bounce back just fine.”

But like just about everything else this season at Citi Field, that didn’t pan out.

Josh Walker was recalled from Triple-A Syracuse to fill Diaz’s spot on the roster. Walker had just been optioned to make room for Wednesday’s starter, David Peterson.