Britton bitten by the short porch in right

Zach Britton relished pitching in the postseason, but he left regretting one pitch.

Britton entered the game to start the top of the fourth after Aaron Boone finally yanked CC Sabathia.

The left-hander, though, immediately gave up a leadoff homer to Christian Vazquez to give Boston a four-run lead.

The shot was a prototypical Yankee Stadium home run, just into the seats in right field — and the extra run came back to haunt the Yankees in their season-ending 4-3 defeat to the Red Sox in Game 4 of the ALDS.

“It’s frustrating,’’ Britton said of what proved to be the decisive run. “I’ve played and pitched here enough to know that porch is short. He got enough just to get it out. It’s a fly out in most places, but knowing that as a pitcher, you’ve got to make quality pitches. There’s no ‘get it over strikes,’ especially since righties are usually looking to shoot the ball to right field against me. He got enough of it.”

The ball traveled an estimated 338 feet, but it did plenty of damage.

Britton recovered to retire six of the next seven batters he faced and the Yankees bullpen didn’t allow another run.

The Yankees got a run back in the fifth to make it 4-1 and then rallied for two more in the bottom of the ninth, when they loaded the bases and Neil Walker was hit by a pitch to force in a run and Gary Sanchez’s sacrifice fly scored another to make it 4-3.

But their late charge came up just short, as Gleyber Torres couldn’t beat out an infield hit to end it.

“It’s even more frustrating because we lost by one,’’ Britton said. “You just want to give the offense a chance. It was good to see them battle back, but the home run was the difference between us going home and going to Boston.”