On the same day the Yankees traded away an important member of their rotation, another who is sticking around created more cause for concern.

With Jordan Montgomery on his way to St. Louis — to be replaced by Frankie Montas — Jameson Taillon struggled again for the Yankees in an 8-6 loss to the Mariners on Tuesday night at the Stadium.

Still, the Yankees did enough to have a chance in the bottom of the ninth.

After DJ LeMahieu singled with two out, Aaron Judge and Anthony Rizzo walked to load the bases for Gleyber Torres, pinch-hitting for Tim Locastro. But Torres struck out to end it.

Still, the Yankees exited Tuesday 70-35 and with an 11-game lead over the second-place Blue Jays in the AL East, confident they were better after the trade deadline.

“I think so and I hope so,’’ manager Aaron Boone said. “[Adding] Frankie Montas, a couple of important bullpen pieces and an elite center fielder and [Andrew Benintendi] a week ago. I think we’re significantly better, but I’ve said all along, we’re better in name only. It’s on us to go prove it.”

Some of that will rest on Taillon, who has mostly pitched poorly in 11 starts since early June. His ERA has jumped from 2.30 following his start on June 2 to 3.96.

“I’m chasing it,’’ said Taillon, who walked a season-high four and gave up two more homers. He has now allowed eight homers over his last six outings.

Despite scoring six runs or more for a fifth straight game — and getting three more homers — the offense couldn’t get Taillon and the bullpen off the hook. Aaron Hicks grounded into an inning-ending double play after the Yankees had tied the game with three runs in the sixth.

The Yankees’ offense came alive in the fourth.

Rizzo walked and, after Matt Carpenter flied out, the slumping Josh Donaldson doubled down the left field line, scoring Rizzo all the way from first.

After Benintendi whiffed, Jose Trevino hit his third home run in two nights to get the Yankees within a run.

Taillon couldn’t make it through the fifth thanks to a pair of walks. Lucas Luetge gave up a two-run double to Carlos Santana after replacing Taillon and allowed a go-ahead homer to Sam Haggerty in the seventh.

Still, the main issue was Taillon, who said he believes the rotation will be solid even in Montgomery’s absence.

“I think it can continue to be a point of strength,” Taillon said. “We’ve had some inconsistency here, but Gerrit [Cole] and Montas coming in, [Nestor] Cortes doing what he’s done all year and [Luis] Severino coming back at some point, there’s a lot to like.”

Rizzo got it back to a two-run game when he hit his 27th homer of the season to start the bottom of the sixth.

Matt Carpenter followed with a single and then Donaldson tied the score with a homer into the Yankees’ bullpen in right-center. It was Donaldson’s first home run since July 8, when he’d gone deep for a third straight game.

The Yankees had a chance to take the lead later in the inning when Trevino greeted Penn Murfee with a double to right-center and Isiah Kiner-Falefa reached on an infield hit to put runners on the corners for Aaron Hicks.

But, batting ninth in the order and in an 0-for-20 skid by the sixth inning, Hicks’ slump worsened when he grounded into his second double play of the game. He was booed loudly after a ninth-inning strikeout.

The Yankees threatened in the eighth, with Carpenter walking to lead off and pinch-runner Locastro moving to second and third on a pair of wild pitches from Matt Brash with two out and Trevino at the plate.

But Trevino struck out looking.

Albert Abreu allowed a run in the ninth to put the Yankees down by two runs again.

The Yankees couldn’t score off five Seattle relievers in 3 ²/₃ innings.