The Yankees are on their way to the postseason.

It’s becoming less and less certain that CC Sabathia will be able to join them there.

The left-hander exited Friday’s 8-2 loss to the Athletics in The Bronx after just three innings and 48 pitches when the pain in his surgically repaired right knee flared up.

No tests were scheduled, likely because none are needed to show the state of Sabathia’s knee, which already has sent him to the injured list twice this season.

The loss was also the Yankees’ fourth straight to the A’s, following last week’s sweep in Oakland. The A’s are in line for the second wild card and would play the Rays in the one-game playoff if the season ended today.

As for Sabathia, it was his third outing since his most recent IL stint and before the game, manager Aaron Boone said they hoped to continue building up the left-hander’s pitch count, as they had in his previous outing.

Instead, he likely will get his knee drained again Saturday and could get another cortisone shot.

He made no guarantees he would return to the mound in his final season.

“I hope so,’’ Sabathia said. “That’s the plan. I hope I get enough rest and it calms down and I’m able to get back out there where I’m able to throw 90-100 pitches.”

Sabathia threw 67 pitches in his first game back, when he struggled against the Indians on Aug. 18. Six days later, Sabathia threw 78 pitches in four innings against the Dodgers and showed some promising signs — including seven strikeouts.

But Friday, he was removed following the third despite a low pitch count and having retired the side in order in the top of the inning.

“It just got bad again,’’ Sabathia said, pointing to one pitch in the third inning, though he didn’t recall who was at the plate.

Even before that, Sabathia knew he wasn’t right — and that went back to his previous outing against the Dodgers in Los Angeles — when he took his third at-bat of the season.

“It was hurting all night [Friday],’’ said Sabathia, who saw team physician Dr. Chris Ahmad after the outing. “When I went up to hit [in L.A.] and took a curveball and I stepped, that started it.”

But Sabathia wasn’t bothered that the latest setback began with him doing something he’s unaccustomed to — hitting.

“It could have happened at any point,’’ Sabathia said. “It just so happened I was hitting.”

He was replaced by Luis Cessa, who threw two scoreless innings before Tommy Kahnle faltered in the sixth.

As they opened a six-game homestand, the Yankees held a 2-1 lead after scoring a run in the third and another in the fourth — when they plated just one run despite having the bases loaded and no out.

Kahnle gave up a game-tying RBI double to pinch-hitter Seth Brown and a two-run, go-ahead double to Jurickson Profar to put the A’s up, 4-2.

The A’s pulled away late and retired 16 straight to end the game.

Boone didn’t make much of the team’s recent struggles against a potential playoff opponent.

“Obviously, Oakland beat us up a little bit out there and got us here,’’ the manager said. “As far as how that affects us moving forward, we’ll see. I don’t worry about that at all.”

Before he left, Sabathia pitched fairly well, allowing a solo home run to Profar with two outs in the second before cruising through the third.

“It’s frustrating, for sure,’’ said Sabathia, who opened the year on the IL after undergoing a heart procedure in the offseason that delayed his comeback from earlier knee surgery and was also shelved because of the right knee in May and July. “Especially because I feel like I can get outs and help the team. That’s the hardest part. And when I am out there I’m not performing.”

And like Sabathia, Boone made no assurances Sabathia would be an option for the rest of the season.

“I hope so,’’ Boone said. “I don’t want to speculate on that. We’ll see how he responds.”