CINCINNATI — Those searching for warts in the Yankees’ bolt toward the top of the American League East six weeks into the season found one to seize on Tuesday night.

CC Sabathia struggled for the fourth straight outing, allowing five second-inning runs in a 5-3 loss to the Reds at Great American Ball Park that ended the Yankees’ six-game winning streak.

“The cutter got better as the game went on,” said Sabathia, who allowed five runs and seven hits in six innings. “In that second inning, for whatever reason, it was leaking back over the plate. I felt good throwing it later in the game. My changeup really kept me in it, so that was encouraging.”

The 36-year-old lefthander, who walked two and struck out two, did allow just one hit over his last four innings, but the Yankees’ offense did not register many big hits after Gary Sanchez and Didi Gregorius hit home runs to give Sabathia a 2-0 lead entering the second.

The Yankees (21-10), who put at least one baserunner on each inning, went 1-for-6 with runners in scoring position and stranded eight. Gregorius’ two-out single after Starlin Castro’s leadoff double in the fourth cut their deficit to 5-3.

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In the ninth, Sanchez, who homered in the first, came up with two on and sent a bullet to third. The lineout turned into a game-ending double play as Aaron Hicks had no chance to get back to second base in time.

“We battled every inning and put up a good fight,” Sanchez said through his translator, “but unfortunately we didn’t get a win.”

Sanchez’s first-inning homer to left was estimated to have traveled 448 feet. That made him 7-for-13 since returning from the disabled list Friday night.

Sabathia (2-2, 5.77) had a 1.47 ERA after his first three starts of the season but was 0-1 with a 10.43 ERA over his next three starts. He chalked those struggles up primarily to difficulty with his cutter.

“He found it tonight, so hopefully it carries over to the next start,” Joe Girardi said. “He kept us in the game. That’s what he does. He competes as well as anyone I’ve ever been around. He’ll find it.”

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Now, for the big picture: Despite the loss, the Yankees, now one-half game behind the Orioles, finished the two-city trip 4-1, with the third of those victories an 18-inning marathon Sunday night at Wrigley Field.

“Really good trip,” said Girardi, whose club is off Wednesday before starting a four-game series against the AL West-leading Astros Thursday night at the Stadium. “What we went through, that’s a really good trip.”

An offense that entered the night leading the league in runs (177), runs per game (5.90), homers (50), OBP (.357), slugging (.463) and OPS (.820) was held in check after the early homers.

Tim Adleman allowed three runs and five hits in five innings for the Reds (18-15). Michael Lorenzen pitched two scoreless innings and closer Raisel Iglesias pitched the final two innings — with the ninth a bit rickety — for his sixth save.

Iglesias walked Hicks and Matt Holliday with one out in the ninth, bringing Sanchez to the plate. He smoked a 97-mph fastball right to third baseman Eugenio Suarez, starting the game-ending 5-4 double play.

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“I hit it well but it was right at him,” Sanchez said. “That’s part of baseball sometimes.”