Mickey Callaway isn’t willing to relegate Edwin Diaz into lower-leverage situations yet. But with Diaz still struggling, reliever Jeurys Familia’s sudden return to form couldn’t come at a better time for the Mets.

The Mets’ 7-4 loss to Washington on Sunday at Citi Field snapped an eight-game winning streak, but Familia’s dominant eighth inning was an auspicious sign and left Callaway suitably impressed.

“I really am. That was a hell of an inning,” Callaway said. “His effort level is right where you want it. He doesn’t have to throw 95, 97 [mph] every pitch, just control your effort level, keep your head on the target, and he did that [Sunday]. And the results are there.

“That’s a turbo sinker he’s throwing up there, and if he executes it you’re going to get swings like [Gerardo] Parra took off him. He’s making huge strides. He continues to work and continues to have faith in himself.”

It wasn’t just Parra that Familia put on the back foot. He struck out the side, fanning Parra, catching Kurt Suzuki looking and fanning pinch-hitter Andrew Stevenson. And it continued a recent resurgence for Familia.

After struggling to a bloated 7.76 ERA through July 5, Familia has turned his season around and pitched to a solid 2.79 ERA in his 13 outings since, working alongside pitching coach Phil Regan, bullpen coach Ricky Bones and pitching strategist Jeremy Accardo.

“[I] just continue working hard, getting here early working with Ricky, Jeremy and Phil going into my bullpen just working on different things, working on mechanics and just pretty much having confidence in my pitches,” said Familia, who has tossed three shutout innings in his last three appearances.

With Diaz mired in a horrible slump — and it got even worse after he coughed up two more runs in the top of the ninth inning on Sunday — the Mets are in dire need of another reliever to step up alongside Seth Lugo and Justin Wilson. Familia is making a bid, thanks to some mechanical tweaks suggested by Bones.

“Yeah, since Ricky’s gotten here he noticed that I was finishing a little bit short. So now I’m finishing a little longer, so now my arm has the opportunity to pretty much reach its point of the release,” Familia said through an interpreter, adding the adjustment has improved his control.

“Yeah, for sure it helps me to just kind of center the pitch, because I’m closer. Whenever I finish my pitch, it’s allowing me to throw strikes.”