SEATTLE — There’s no stopping Gary Sanchez.

The Yankees, though, are a different story.

The rookie catcher smacked two more home runs Monday night in a 7-5 loss to the Mariners, as the Yankees continue to fall behind in the postseason race.

“It’s hard to explain,” Sanchez said through a translator of his hot start. “I’m just trying to put a good swing on the ball, and I’m getting good results.”

The same can’t be said of the bullpen, which had done well immediately following the departure of Aroldis Chapman and Andrew Miller but has sprung some leaks of late.

After Michael Pineda left with two on and one out in the sixth, Tommy Layne got Adam Lind to pop out, but Anthony Swarzak hung a 3-2 slider to Mike Zunino, who made him pay with a three-run homer to put the Mariners ahead, 6-5.

“I tried to execute my slider, and I didn’t make the pitch,” Swarzak said. “We need every game now, especially with an offensive showing like that.”

Sanchez recorded his second multi-homer game in a week and has 14 hits in his last 25 at-bats, along with four walks.

And on Monday, the Yankees got another two home runs from Starlin Castro — but it still wasn’t enough.

Manager Joe Girardi had hoped Pineda could get the Yankees through six innings, in part because Adam Warren was unavailable thanks to a heavy recent workload.

Pineda, though, struggled with his fastball command and was done in by a 3-0 fastball he threw to Kyle Seager, who hit a three-run homer to give the Mariners a 3-2 lead in the fourth.

“I didn’t do my job,” Pineda said of his 5 ¹/₃-inning, five-run performance.

Girardi was forced to go to his pen earlier than he would have liked. He had planned on going to Tyler Clippard and Dellin Betances to get the last nine outs of the game, but Pineda and Swarzak had lost the lead by then.

“He got to the count he wanted, he just wasn’t able to put him away,” Girardi said of the struggling Swarzak. “But the problem is not getting Michael through six [innings].”

And he refused to blame their recent woes on the loss of Chapman and Miller.

“The bullpen is different, but we’re also scoring more runs now,” Girardi said.

Thanks in large part to Sanchez, who is doing what he can to keep the Yankees alive.

On the day he became the first Yankees catcher since Thurman Munson to be named American League Player of the Week, Sanchez hit homers seven and eight in the last two weeks.

“He’s done an unbelievable job,” Girardi said of Sanchez’s seven-game stretch.

But not even three more hits from the 23-year-old would do the trick. Nelson Cruz gave the Mariners some insurance in the eighth with a solo homer against Kirby Yates.

The Yankees threatened in the ninth, getting the potential tying runs on base, but Mark Teixeira, pinch-hitting for Tyler Austin, flied out to left, and Brett Gardner grounded out to ex-Yankee Robinson Cano at second for the final out of the game.

“These are games you’d like to win,” Girardi said. “But we couldn’t put it all together.”

And a day after they wasted a fine pitching performance by Chad Green, another memorable night at the plate by Sanchez went for naught.

If the Yankees get their way, though, there will be plenty more from Sanchez.