Dellin Betances of the New York Yankees gets set to...

Dellin Betances of the New York Yankees gets set to pitch in the seventh inning against the Boston Red Sox at Yankee Stadium on Thursday. Credit: Jim McIsaac

Rain interrupted, and not rudely from the Yankees’ perspective, CC Sabathia’s worst start of the season.

And though the Yankees took him off the hook with the kind of late-inning rally they have featured so often during the last three weeks, they couldn’t do the same for Dellin Betances.

Betances, pitching a second inning after a perfect seventh, allowed a leadoff homer in the eighth by J.D. Martinez that sent the Yankees to a 5-4 loss to the Red Sox on Thursday night in front of 46,899 at the Stadium.

The loss, which snapped an eight-game winning streak, was only the second in 19 games for the Yankees (26-11), who dropped back into a tie atop the AL East with their rivals.

Said Aaron Boone, “You walk off there disappointed, but again, also proud of the way the guys continue to compete through the end and give ourselves a chance on a night when maybe it doesn’t look that way. It’s a tribute to those guys, but yeah, every time you leave something out there, you think about what-ifs and all that.”

Martinez’s ninth homer barely cleared the rightfield wall. Aaron Judge drifted to the track and jumped, but the ball eluded his glove and nestled snugly into that of a fan’s.

Was fan interference a factor? “I ran into him [the fan], but once you get past that line, it’s fair game,’’ Judge said. “For me, if I get a better read and jump at the right time and get in a better position, I make the play. That’s what it comes down to.”

Said Betances, “I was hoping it stayed in in that situation. I don’t know how he got it like that, but he got it. The pitch was probably a ball in and he inside-outed it. Probably not a home run in any [other] park, but it’s a home run today. It’s tough, but tomorrow’s another day.”

Joe Kelly got out of a jam in the bottom of the eighth, striking out Neil Walker with runners on first and second. That set up a rematch between Craig Kimbrel and the Yankees’ top of the order in the ninth. Kimbrel, who allowed Brett Gardner’s two-run triple and Judge’s two-run homer into Monument Park in a four-run eighth Wednesday night, started Thursday’s outing by striking out Gardner with a 97-mph fastball. Judge flied softly to center and Didi Gregorius grounded out to end it, extending his slide to 0-for-25.

Said Judge, “He made his pitches when he had to. He got behind Gardy, he got behind me a little bit, but when it was on the line, he made his pitches when he had to. That’s the definition of what a closer does. That’s why he’s been so successful all these years. Just mentally tough.”

With one out in the seventh, Miguel Andujar singled, Gleyber Torres flared a checked-swing single to right and Walker walked to load the bases. Gardner walked on four pitches to make it 4-1 and Judge singled to left for another run. Gregorius chopped one to second for a forceout, with Walker scoring, and with Giancarlo Stanton at the plate, Kelly threw a wild pitch that made it 4-4.

“Their at-bats here after the seventh inning, it’s just amazing,’’ Sox manager Alex Cora said. “What they’ve been doing here, for them, it’s fun to watch. For me, it’s like, ‘Oh, God, here we go again.’ ”

Sabathia allowed a leadoff home run by Hanley Ramirez in the fifth that put the Yankees in a 4-0 hole. After he delivered a strike to Martinez, heavy rains doused the Bronx and at 8:47 p.m., the tarp was pulled onto the field.

After a 55-minute delay, the game resumed, with Sabathia replaced by Jonathan Holder.

Sabathia, who had been 2-0 with a 1.39 ERA in six starts this season, including 2-0 with a 0.39 ERA in four starts since returning from the disabled list April 19, allowed four runs and nine hits in four innings-plus.

Eduardo Rodriguez, who entered the game with an unimpressive 5.29 ERA this season but was 4-2 with a 2.96 ERA in nine career starts against the Yankees, pitched five shutout innings, allowing one hit. He walked three and struck out eight.

Given the way Sabathia had pitched this season, his outing was unexpected.

“He’s made the transition, obviously, with less stuff but no less ability to pitch,” Boone said before the game, referencing Sabathia’s transformation from being a power pitcher. “The cut fastball for him has been a game-changer. It’s allowed him to consistently get righthanded hitters out. I talk about the athleticism of CC all the time and his ability to repeat his delivery, but that cut fastball has just set up his breaking ball, his changeup. It’s been a lot of fun to watch him go out and do his craft, if you will. He’s really in a good place and pitching with a lot of confidence.”

But Thursday turned out to be one of those nights every player experiences during the grind of the long season. And it was apparent early.

Mookie Betts led off the game by driving a full-count slider to right for a double and went to third on Andrew Benintendi’s groundout. When Ramirez grounded sharply to short, Gregorius thought about throwing home but instead went to first, and the Red Sox led 1-0.

The Red Sox tacked on two more in the third to make it 3-0, and Ramirez’s homer to beat the rain made it 4-0.

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