NEW YORK — The Yankees have to be concerned about left-hander Nestor Cortes. Once a stalwart in the rotation, Cortes is not giving the club enough length to win games and he is getting hit hard. Including Thursday’s 9-4 loss to the Angels at Yankee Stadium, Cortes has allowed 28 earned runs in his past 33 2/3 innings.

Manager Aaron Boone believes Cortes is healthy and “the stuff is there.” It just comes down to executing his pitches. For Boone, there is a different story for each of those seven starts.

“There were a few starts … where it wasn’t great. A couple [of starts] where he didn’t have that extra gear on his heater,” Boone said.

What’s the story for Thursday’s game? Conditions on the field were impacted by the rain and Cortes had a tough time gripping the ball.

“When the rain is on you and you are trying to grip the ball, you have 15 seconds [because of the pitch timer] and it’s just tough to go into your glove,” Cortes said. “And if they call for another pitch that you are not gripping and go to it, it’s tough. It’s no excuse. Both teams had adversity. The Angels were a better team today.”

One thing Cortes couldn’t do against Los Angeles was get quick outs. He retired the side in order just once while allowing six runs in 4 2/3 innings. His worst frame came in the fifth, with New York already down, 2-1, as Los Angeles had things go its way against Cortes.

Cortes had recorded two outs over the first three batters, but he couldn’t end the inning, as the Angels ended up scoring six runs in the frame. The next two hitters — Zach Neto and Logan O’Hoppe — both reached base before Kevin Pillar singled home a pair of runs.

Cortes left the game in favor of right-hander Enyel de los Santos, who fared no better as he allowed a bases-clearing double to Jo Adell, who would later score on a single by Mickey Moniak to make it a seven-run game.

Boone came away thinking that Cortes didn’t have that bad of an outing. The skipper liked how Cortes looked mechanically.

“You look up today, the profile was good. The Angels did a good job putting the ball in play,” Boone said. “They didn’t sting the ball a ton against him. But especially with two strikes, they were able to touch it and put it in play and dumped some balls out there that just created traffic and some problems.

“Tonight wasn’t our night,” Boone said. “I actually thought Nestor threw the ball OK. He wasn’t giving up a lot of hard contact, but he had a hard time putting guys away. [The Angels] were spoiling pitches. [Cortes] would get two strikes, and he couldn’t finish guys off.”

With the exception of Jazz Chisholm Jr., the Yankees couldn’t touch left-hander Tyler Anderson, who lasted six innings and allowed one run on three hits while striking out seven. That lone run off Anderson came in the second inning, when Chisholm hit his first Yankee Stadium home run as a member of the team.

“Tonight, he was on,” Boone said about Anderson. “… You watch it from the side, that changeup was excellent. It had enough life and he was getting the fastball to cut at times to good spots. I thought Anderson was on top of his game tonight.”