October 7, 2020 | 2:09am

J.A. Happ’s contentious season with the Yankees got even rockier on Tuesday after the left-hander struggled in a relief appearance in Tuesday’s 7-5 loss in Game 2 of the ALDS that tied the series at 1-1.

Happ clearly wasn’t pleased with the team’s plan to have him piggyback Deivi Garcia out of the bullpen to start the bottom of the second inning and the 37-year-old didn’t pitch well, allowing four runs in 2 ²/₃ innings at Petco Park in San Diego.

He hadn’t pitched since Sept. 25, having not been used in the wild-card series against Cleveland.

Happ said he couldn’t “quantify” how the time off might have impacted, adding, “I don’t think they [the Yankees] can, either.”

Aaron Boone said throughout the season, Happ hadn’t been affected by time off, saying “for the most part, he’s done really well in whatever situation.’’

That wasn’t the case at times — and it wasn’t on Tuesday.

Asked about the Yankees’ peculiar plan of starting the inexperienced Garcia and pulling him after just one inning to go to the veteran Happ, the southpaw repeatedly declined to comment.

J.A. Happ
J.A. HappCorey Sipkin

“I’ll let Aaron [Boone] speak to that [strategy],’’ Happ said.

But he did say he would have preferred to have started the game if he was going to pitch and Happ added the team knew that was the case.

“When I’m in there, you’ve got 100 percent of me,’’ Happ said. “I wasn’t worrying about when I was coming in.”

He added he was “initially” surprised by the plan, but took ownership of his poor outing.

“I didn’t get into a groove,’’ Happ said. “I wish I could have performed better, for sure.”

Happ allowed a two-out, two-run homer to Mike Zunino in the bottom of the second and then another two-run shot to Manuel Margot an inning later to put the Yankees in a 5-1 hole.

He also made an error in the third, but managed to prevent further damage by retiring Kevin Kiermaier and Zunino with two on.

And he got knocked out in the fourth. After getting the first two batters of the inning, Happ gave up another hit to the red-hot Randy Arozarena and then a walk to Ji-Man Choi before he was pulled in favor of Adam Ottavino, who got pinch-hitter Yoshitomo Tsutsugo to fly to left.

Throughout his rocky 2020 season, Happ pitched far more effectively on regular rest after expressing his displeasure with the Yankees for what he thought was an effort to manipulate his innings to prevent him from hitting incentives that would allow his $17 million option for next season to vest.

Over a six-start stretch before his final appearance of the regular season, Happ had a 1.93 ERA and Boone said on Monday the 37-year-old had been as good as any starter on the team during that period.

“I’ve been here for two years and if anyone has heard me make an excuse for my performance in two years, they can speak up,’’ Happ said. “It didn’t happen. I’m not gonna make an excuse.”