Batting from the left side, Walker golfed a no-doubter in the seventh inning off Ryan Brasier for the Yankees’ third hit of the game and a 3-1 lead. Walker dropped his bat, admired the shot for a moment and then pointed into the Yankees dugout as he jogged to first base.

Aaron Judge returned to New York’s lineup for the first time since breaking his right wrist July 26, while AL MVP candidate Mookie Betts got a day off for Boston after injuring his left side Sunday. Judge hit a pop fly to the warning track but finished 0 for 4.

New York entered the night with a 1 1/2-game lead over Oakland for the top AL wild card. The A’s hosted the Angels later.

Boston is trying to clinch the AL East at Yankee Stadium for the second time in three years. The Red Sox lead the Yankees by 10 1/2 games and entered the night with a magic number of four over the Astros to lock up baseball’s best record.

The game started about six hours after it was supposed to begin. Originally scheduled for 1:05 p.m., it was pushed back earlier in the morning because heavy rain was in the forecast.

Britton had two on in the ninth after Brock Holt walked and Christian Vazquez reached when second baseman Gleyber Torres was unable to handle a wide feed from third on the first potential game-ending double play. Britton then scooped a short grounder by Sam Travis and threw it into center field with runners at first and third, allowing Holt to score. Ian Kinsler followed with an almost identical ball back to Britton, and the left-hander hit the target this time for the final two outs.

The Yankees had dropped 10 of 17, including a series defeat to Toronto over the weekend capped by Dellin Betances’ blown save in the eighth inning Sunday.

The bullpen had no such issues against their archrival. Chad Green (8-2) and David Robertson relieved J.A. Happ and got the ball to Britton, who capped a five-hitter for his sixth save.

Boston reliever Brandon Workman (6-1) walked two in the seventh before Walker took Brasier deep. The Red Sox bullpen wasted six scoreless innings of two-hit ball from hard-throwing starter Nathan Eovaldi.

Happ was nearly as good in muffling the Red Sox once again, allowing an unearned run over six innings. He entered as one of only four pitchers since 1923 to allow two or fewer earned runs over 10 straight starts against Boston — the others were Gaylord Perry, Randy Johnson and Bruce Howard. Happ has a 1.76 ERA in his past 11 starts against the Red Sox.

Boston went ahead 1-0 with an unearned run in the third. Ian Kinsler reached on a single, took second on Happ’s balk, went to third on a passed ball by Gary Sanchez then scored on a sacrifice fly to right by J.D. Martinez.

Sanchez was booed after grounding out weakly to the pitcher in the fifth inning. He went 0 for 2 with a walk.

Walker’s home run was his 10th, giving New York 11 players with double-digit homers. That ties a major league record, last achieved by Houston last season. Luke Voit has seven homers and is probably the Yankees’ best bet to break the mark.

STAR-CROSSED

Betts would have played if not for the soggy conditions. Manager Alex Cora wrote Betts in as his center fielder at 9 a.m. but scratched him when it became clear the weather would be an issue.

Meanwhile, Yankees manager Aaron Boone slotted Judge to bat second and play right field, but only because the late start gave him and the front office a few extra hours to evaluate the reigning AL Rookie of the Year.

Judge hit an opposite-field homer to right during a series of simulated plate appearances against Yankees minor leaguer Adonis Rosa on Tuesday morning. Judge was late on some fastballs and had a number of swings and misses against Rosa, who struck out 108 over 128 1/3 innings across three minor league levels this season. A large contingent of Yankees personnel watched the session, including Boone and general manager Brian Cashman.

A good portion of the Yankee Stadium crowd stood for Judge’s first at-bat. Fans gasped when he hit a hard line drive into right field, then exhaled and clapped after Martinez easily caught it. The lineout was measured at 112 mph.

Judge hit into an inning-ending double play in the third, then drove a fly out to the warning track in the right field corner in the sixth.

JUSTUS SERVED

Top prospect Justus Sheffield was activated by the Yankees and available in the bullpen. The left-hander was moved to the bullpen at Triple-A Scranton/Wilkes-Barre in late August as preparation for a possible call-up as a reliever. Right-hander Domingo German was also recalled from Triple-A.

TRAINER’S ROOM

Red Sox: Matt Barnes (hip inflammation) is set to throw a bullpen Wednesday and be re-evaluated after that. … Eduardo Nunez started at DH and said he is fully healed after experiencing right knee soreness late last week.

Yankees: Aroldis Chapman will likely be activated Wednesday or Thursday. The closer has been out since Aug. 21 with left knee tendinitis.

UP NEXT

Red Sox left-hander David Price (15-6, 3.42) faces struggling Yankees ace Luis Severino (17-8, 3.46). Price is 5-0 with a 1.56 ERA in nine starts since the All-Star break, while Severino has a 6.35 ERA in 10 starts over that same span.