SEATTLE — After talking about their October dreams on Wednesday night, the Yankees faced a potential nightmare scenario on Thursday afternoon.

Their playoff hopes flashed before their eyes when Juan Soto chased down a high ball in right foul territory and slid into the wall to make a great catch, but he was left lying on the ground in pain.

He threw the ball back into the infield, tossed his glove away and tended to his left knee, which he had smacked into the concrete beneath the padding.

Aaron Boone, two coaches and a handful of concerned teammates ran to the right to check on Soto. Eventually, Soto got up and stayed in the game.

The Yankees and Soto appear to have nothing more serious than a bruise and some swelling in his knee. That’s a win, as they lost 3-2 to the Mariners and missed out on a sweep at T-Mobile Park.

“(I was) really worried,” Soto said after receiving treatment nearly an hour after the game. “When I threw the ball in, my kneecap was hurting a lot. But as time went on, it got better and I felt better. I was really a little scared.”

Soto would have X-rays taken as a precaution to make sure he had not damaged his knee.

He said how he wakes up Friday in Oakland and what the swelling is like will determine whether or not he’s in the Yankees’ lineup against the A’s.

“Your heart definitely skips a few beats and I’m sure all the Yankees fans around the world felt the same thing,” said Clarke Schmidt, who allowed three runs (one earned) in five innings and was in the training room when the action occurred.

The loss, combined with the fact that the Orioles finally won a game earlier on Thursday, cuts the Yankees’ lead atop the AL East to four games with nine games remaining.

Their magic number to win the division remained six.

On Thursday, less than three hours before first pitch, a large group of Yankees arrived at the visitors’ clubhouse, still smelling of cheap champagne and beer from the night before.

But if that didn’t have a negative impact, it was the Mariners’ strong pitching that did. The Yankees (89-64) went just 1-for-12 with runners in scoring position against right-handed pitcher Logan Gilbert and Seattle’s bullpen.

They left eight runners on base and their only source of offense was a two-run home run by Jazz Chisholm Jr. in the third inning against Gilbert.

Those woes, coming a day after they became the first American League team to clinch a playoff spot, would pale in comparison to losing Soto for an extended period with the playoffs just two weeks away.

The play was reminiscent of Aaron Judge running into the unlined portion of the right-field wall at Dodger Stadium last year, injuring his toe and jeopardizing the Yankees’ season.

But Boone said he thought the way Soto slid might have saved him.

“My biggest fear was that he twisted something,” Boone said. “I think sliding like that saved him a little bit, he banged his knee pretty good.”

Soto has struggled with hand and foot injuries this season, but played his 149th game in the Yankees’ 153rd game of the year on Thursday.

He has a huge payday waiting for him on the free agent market this offseason, and the Yankees are confident of a playoff run, but that didn’t stop him from trying to make a playoff berth in a one-run game.

“I feel like it’s just the adrenaline of the game,” Soto said. “You talked about free agency, this and that — when I get in those lines, I forget about everything. I literally just focus on the game. We’re trying to win the game to help the team do the best it can.”

The Mariners took a 3-0 lead off Schmidt in the first inning after Jasson Dominguez dropped a fly ball to left field, struggling to catch the ball in the sun. It was his second defensive blunder in as many days.

Then, after a double in the second inning, Dominguez was eliminated trying to score from second base on a line-drive single from Anthony Volpe to right fielder Luke Raley.

“It’s a bang-bang play on a perfectly executed pitch from Raley,” Boone said. “It’s the second inning, so you can’t just sit there and do nothing. You’ve got to play the game. So no problem (with the send).”