WASHINGTON — It took a bogus triple play and a blown ninth-inning lead for the Mets’ seven-game winning streak to come to an end on Friday night.

The Mets lost to the Nationals, 5-4, as Washington scored two runs in the bottom of the ninth off Ryne Stanek — a curious fill-in for closer Edwin Diaz — and A.J. Minter.

Trailing 3-0 in the eighth, the Mets rallied for four two-out runs on an infield RBI single by Brandon Nimmo and a go-ahead, three-run triple by Mark Vientos.

But when the bullpen door swung open in the bottom of the ninth, Stanek and not Diaz came out. Manager Carlos Mendoza had said before the game that Diaz was “fine” after leaving Wednesday’s game against the Phillies with a hip cramp.

Stanek gave up a leadoff triple to deep right to Dylan Crews and a tying single to Jose Tena.

Two forceouts later, Minter gave up a single to James Woods that glanced off the glove of second baseman Jeff McNeil and into short centerfield. CJ Abrams raced around from first and scored the walk-off run. The Mets challenged the safe call at home but the replay umpires quickly confirmed the game was over and the Nationals had won.

In the fourth, the Nationals pulled off a controversial triple play. Except it shouldn’t have been — the umpires blew the call.

The Mets were trailing 2-0 with Brandon Nimmo on second and Vientos at first.

Jesse Winker lined a ball to first baseman Nathaniel Lowe, who appeared to trap it. But first base umpire Alfonso Marquez signaled out, ruling that Lowe had caught the ball on the fly.

Lowe threw to second to double off Nimmo, who was on his way to third base. Shortstop Abrams caught the ball while on the bag for the second out. Abrams tagged Vientos, who was standing on second, for the third out. The play was scored 3-6-6.

Mendoza was incensed and argued that the ball had been trapped. Replays backed him up.

But a ball that is either caught or trapped on the infield is not reviewable under MLB’s replay rules. Only a ball hit to the outfield.

So the call stood. And the inning was over.

It will go into the record books as the 11th time in franchise history the Mets hit into a triple play.

McNeil and Francisco Alvarez made their season debuts after being activated off the injured list. Both went 1-for-4. McNeil had been out with an oblique injury and Alvarez was sidelined with a broken bone in his left hand.

Kodai Senga saw his scoreless streak end at 20 1/3 innings when Washington took a 1-0 lead in the second. With two outs and no one on, Crews grounded a single to left. But Nimmo, for some reason, threw the ball in the direction of third base. When Crews saw that, he took off for second. It was initially scored a double, then was changed six innings later to a single (second on the throw). Jose Tena followed with an RBI single.

Abrams made it 2-0 with an RBI triple off the centerfield wall in the third.

Senga, who went six innings, allowed two runs and six hits, walking two and striking out five.

Abrams added an RBI infield single off Huascar Brazoban in the seventh to make it 3-0.