BOSTON — Andrew McCutchen swung and missed the first pitch Friday night.

The radar gun reading on Fenway Park’s scoreboard flashed a 96.

All was good for the Boston Red Sox, for the moment.

Chris Sale followed that 96 mph fastball with one recorded at 94. Then he froze McCutchen on an 81 mph slider for Strike 3.

That’s one big sigh of relief over Sale’s health and velocity.

What followed was an even bigger exhale after Boston escaped with a 5-4 win, beating the New York Yankees in Game 1 of their American League Division Series.

Sale left with a 5-0 lead, with two runners on base, and one out in the sixth inning.

Over the next 10 New York batters, Boston’s bullpen allowed three hits, three walks and three RBI.

Shaky ground.

The situation forced Alex Cora to use starter Rick Porcello in eighth inning, and call on closer Craig Kimbrel for a four-out save.

“To get 27 outs at this stage right now is very difficult,” Cora said. “We had an idea Rick was going to be in a bullpen … Sometimes, you have to go to plan B or plan C.

“In a perfect world, the starter goes six. You have the seventh inning guy, eighth inning, and ninth inning, and you move on.”

This is hardly a perfect world for the Boston bullpen. Ryan Brasier allowed both inherited runs to score. Brandon Workman and Matt Barnes were good and bad.

Two factors saved the Red Sox: That 5-0 lead, thanks in part of J.D. Martinez’s three-run home run – and New York’s lack of clutch hitting.

With the score 5-2, New York loaded the bases with two outs in the sixth. Workman escaped by striking out Gleyber Torres, swinging at a full-count curveball out of the strike zone.

In the seventh, the Yankees loaded the bases with no outs – two singles off Workman, and a walk by Barnes. But Barnes struck out Giancarlo Stanton and induced two groundouts, allowing only one run.

“We made some pitches,” Cora said.

Two squanders for New York; part of 10 men left on base.

“They did a good job of minimizing and staying away from trouble against us,” Yankees manager Aaron Boone said.

“But, yeah, we just couldn’t get that really big hit, to have that big inning.

“I thought we did a good job of pecking away … just ran out of time.”

The last “peck” was an Aaron Judge homer to lead off the ninth against Craig Kimbrel.

Boston did not use knuckleball pitcher Steven Wright because his knee is sore again (status TBA).

Another starter, Nathan Eovaldi, was available, but Cora said he liked the match-ups with Porcello.

Porcello was supposed to start Game 3. But Cora can’t wait for later games, especially if his bullpen is going to deliver the kind of performance Friday night.

“We’ll talk about it,” Cora said. “You might say (plan) C and a half.”

The good news if that Sale was dealing. He did give up five hits and those two runs, but he gave Boston enough.

“I thought he was good,” Boone said. “Not his dominant self, necessarily.”

Sale used a lot more sliders and change-ups.

“That’s part of the game, changing speeds and eye levels,” Sale said. ”

“There’s no holding back now. It’s everything on the table, everything you’ve got.”

By the sixth, Sale looked tired. He gave up a hard-hit, line-drive single to Judge. After Judge would have been Aaron Hicks (who walked and singled already against Sale), but he had injured his hamstring. Brett Gardner filled in and grounded into a fielder’s choice. Stanton followed with a hard-hit single, and Cora came for Sale, after 93 pitches.

Short outings may be the postseason trend, but Boston’s bullpen makes that nerve-wracking.

Boston won on Friday because the Red Sox were able to ounce on starter J.A. Happ, who was “just not having his real airtight command that he usually has,” Boone said.

J.D. Martinez stroked an inside fastball for a first-inning, three-run homer. Mookie Betts and Andrew Benintendi reached in the third, with no outs. Happ exited, and both Betts and Benintendi eventually scored.

New York’s bullpen kept the game in reach with six scoreless innings.

“That’s one of our ultimate strengths,” Boone said. “If we’re going to get where we want to go, the bullpen is going to play a big role in that.”

Cora is still trying to figure out what his pen can do. He’ll use a starter here and there and hope matters fall into place.

Boston will count on big hits (Martinez and company) and solid fielding (Betts ran down a slicing line drive in the third inning with a runner on, and catcher Sandy Leon was blocking balls in the dirt all night).

As for the relief pitching … be ready for more white-knuckle adventures.