SEATTLE – Taijuan Walker’s return Tuesday to the Mariners’ rotation mirrored his season. There were tantalizing moments of promise that faded into disappointment. And a 5-1 loss to New York Yankees.

Walker permitted just one hit through four innings, although that hit cost him a run, but he started the fifth by yielding a line-drive double to Ronald Torreyes.

Then came a two-run homer by Jacoby Ellsbury, whom Walker had struck out in two previous at-bats. The Yankees had a 3-1 lead, added another run in the sixth inning, and that was it.

New York veteran lefty CC Sabathia (8-10) delivered a turn-back-the-clock effort in limiting the Mariners to one run and three hits in seven innings before Tommy Layne and Dellin Betances closed out the victory.

So it wasn’t just Walker. A punchless attack gets a portion of the blame. So, too, does a defense that coughed up two unearned runs.

The combination resulted in a loss that dropped the Mariners to two games behind Baltimore in the race for the American League’s final wild-card berth with 37 games remaining.

The Mariners recalled Walker (4-8) earlier Tuesday from Triple-A Tacoma, where he had served a two-start remedial tour after a disappointing Aug. 6 effort against the Angels.

Walker balked at the demotion, which came after he made just one start following a month-long stay on the disabled list because of tendinitis in his right foot.

Even so, he pitched well at Tacoma, which made him the obvious choice when an injury-thinned rotation forced the Mariners to sift through possibilities for a starting pitcher.

So this was an opportunity. A wasted one. Walker gave up four runs (three earned) in 5 2/3 innings. Not awful. Just not what he or the Mariners needed.

The game’s first run scored after two-out error by third baseman Kyle Seager in the second inning. Walker then walked Aaron Hicks before Torreyes yanked an RBI double to left.

Walker limited the damage to one run by striking out Jacoby Ellsbury with runners at second and third.

Sabathia retired the first seven Mariners before Leonys Martin flicked a drive into the right-field corner that bounced away from Aaron Judge for a one-out triple in the third inning.

Ketel Marte sent a broken-bat grounder up the middle through a shortened infield for an RBI single, which tied the game at 1. The Mariners got nothing more.

Walker had allowed only the one hit before Torreyes opened the fifth with a near-identical double to left. Ellsbury then followed by driving a 94-mph fastball over the right-field wall for a two-run homer.

The Yankees boosted their lead to 4-1 in the sixth after Mark Teixeira’s leadoff double. He went to third on a grounder and scored on Judge’s sacrifice fly.

New York’s final run came against Wade LeBlanc in the ninth inning after left fielder Guillermo Heredia turned Ellsbury’s leadoff liner into a two-base error. Didi Gregorius followed with an RBI double.

Early Christmas present

Right-hander Hisashi Iwakuma is about to cash his Christmas bonus.

Iwakuma needs to pitch just five innings Wednesday – or at any point through the remainder of the season – to lock in a $14 million vesting guarantee for next season.

Under Iwakuma’s contract, signed last Dec. 18, the Mariners hold a $10 million option for next season (with a $500,000 buyout), but that shifts to a guaranteed contract for $14 million if he pitches 162 innings.

Iwakuma enters Wednesday’s start against the Yankees at 157 innings.

“I don’t know where we’d be without him,” M’s manager Scott Servais said. “You look at it, you see it and you’re watching it and you think, ‘How is he doing it?’ But he pitches. He really pitches. It’s the curve. It’s the slider. It’s the split.

“If you look at any one of his four pitches in a vacuum, they’re probably average. But when you put them all together, with his deception and his ability to make pitches, it plays up.”

Iwakuma is 14-8 with a 3.78 ERA in 25 starts. He leads the Mariners in victories, starts, innings and strikeouts. His steady presence allowed the club to weather injuries to every other member of the season-opening rotation.

“That’s part of my job,” he said in early July with Felix Hernandez on the disabled list. “I’m the No. 2 guy. With the King out, we have to stay patient and step up until he comes back.

“When he comes back, I know it’s going to be a lot easier for us.”

The Mariners appeared to lose Iwakuma last December when he agreed to a free-agent deal with the Los Angeles Dodgers for $45 million. The Mariners roughly matched the financial package but weren’t willing to guarantee a third year.

When the Dodgers backed away from their agreement after examining the results of Iwakuma’s physical examination – for reasons that still aren’t clear – Iwakuma and the Mariners resumed negotiations.

General manager Jerry Dipoto announced the deal at the club’s Christmas party. It only guaranteed one year but included club options for two additional years that could turn into guarantees based on performance.

The total package had the potential to exceed the Dodgers’ guarantee and, at that point, Iwakuma was willing to bet on himself.

“I feel very confident,” he said in December. “This is the place that I’ve been able to pitch for the last four years. Obviously, I’m going to take one year at a time and let the rest take care of itself.”

Iwakuma has already triggered a $500,000 performance bonus this season to his $12 million guaranteed deal by reaching 150 innings. He gets another $500,000 each if he reaches 160, 170, 180 and 190 innings.

All are within reach.

The third year in the contract, 2018, becomes guaranteed if Iwakuma pitches 162 innings next season or reaches a 2016-17 total of 324 innings. Right now, that seems a good bet.

Two other free-agent signings, outfielder Nori Aoki and catcher Chris Iannetta, face bigger challenges to trigger their contract clauses with, entering Tuesday, 38 games remaining in the season.

Aoki can trigger a vesting option next season for $5.5 million by reaching 480 plate appearances. Through Monday, he had 379.

Iannetta can convert a $4.25 million club option for next year into a guaranteed deal by starting 100 games. He is currently at 79 but has started only 10 times since the Mariners recalled Mike Zunino on July 20 from Triple-A Tacoma.