SEATTLE — CC Sabathia isn’t a dominant No. 1 starter anymore.

That much has been obvious for the past few seasons. Injuries, workload and personal issues have taken their toll over time. He entered Tuesday night’s start with a 7-10 record and a 4.41 earned-run average and hadn’t allowed less than two runs in his 11 previous starts, dating to June 16. During that span he’d posted a 6.78 ERA and a 2-6 record.

But for Sabathia, 36, pitching against the Mariners has been a cure to many past problems. That trend continued at Safeco Field. The big lefty led the Yankees to an easy 5-1 win, pitching seven innings and giving up one run on three hits with a walk and seven strikeouts.

“Our offense got shut down,” manager Scott Servais said. “That’s the first time that’s happened in a long time. I have to give credit to Sabathia. He threw the ball really well.”

With the win, Sabathia is 13-7 with a 2.64 ERA in 26 career starts vs. Seattle. That ERA is lowest of any American League team that Sabathia has faced in his 16-year career.

“Nasty slider, two-seamer, velocity at 93-94,” said Robinson Cano, who played five years with Sabathia. “It’s the same guy I know. He’s really tough when he’s hitting his spots. He knows how to pitch and he knows how to battle.”

Seattle can’t seem to push past 10 games over .500, falling to 67-58 and dropping two games back in the race for the second wild card in the American League.

Using good command to both sides of the plate, Sabathia carved up the Mariners, breaking at least four bats while limiting any hard contact. He allowed just two base runners over his final four innings.

“That was textbook pitching 101,” Servais said. “Back and forth and changing speeds, on the edges and pitching inside. He was very effective. We got beat. That happens.”

It was the type of outing the Mariners were hoping to get from starter Taijuan Walker in his return to the big leagues after a two-week hiatus at Class AAA Tacoma. The young right-hander showed signs of his potential, but like so many past outings this season, he failed to make it to the seventh inning or even out of the sixth.

Walker (4-8) worked 5 2/3 innings, giving up four runs (three earned) on six hits with three walks and five strikeouts.

“As far as hanging in there, making pitches and continuing to go after them, I thought it was fine tonight,” Servais said.

Walker’s biggest mistake came in the fifth inning. After giving up a leadoff double to Torreyes, Walker threw a regrettable 1-1 fastball to Jacoby Ellsbury over the middle of the plate. The veteran Yankee outfielder had struck out in his two previous at-bats against Walker, but he didn’t miss the mistake pitch, launching it into the right-field seats for his sixth homer of the season to give the Yankees a 3-1 lead.

“I was trying to go up and away,” Walker said. “I had success with it early against him, but it came back over the plate.”

In past outings, that two-run homer might have caused him to crumble. But Walker pitched his way out of the fifth, retiring the next three hitters.

But the damage was done and Walker screamed his frustration into his glove as he left the mound.

He wouldn’t make it out of the sixth, giving up another run and leaving with two outs and two men on.

“My stuff was good and my fastball was a lot better -— velocity-wise and the life on it was better,” he said. “The command was better. I felt like I competed and battled. I got into some jams and kind of got out of them.”

M’s activate Zych from DL

The Mariners returned to a seven-man bullpen before Tuesday’s game vs. the Yankees, activating reliever Tony Zych from the 60-day disabled list. He fills the open spot on the Mariners’ 40-man roster. To make room for Zych on the active 25-man roster, outfielder/first baseman Stefen Romero was optioned back to Tacoma.

“We needed to get back to a full bullpen,” manager Scott Servais said. “Tony has been throwing the ball really well. I don’t think you’ll see him go three days in a row. But he’s had multiple outings on his rehab. He feels good and the reports have been good.”

Zych has looked strong in four rehab appearances throughout the Mariners’ minor league system, not allowing a run in four innings pitched. His fastball has been clocked as high as 98 mph. He’s been on the disabled list since May 3 with tendinitis in his rotator cuff. He was moved to the 60-day DL on June 24. Zych made 10 relief appearances to start the season, posting a 3.00 ERA with 19 strikeouts in 12 innings pitched.

“It’s good,” he said. “I’ve weathered through it. It’s better now. Everything is good. The velocity has been good. I’m ready to go out there and see what happens.”

The shoulder issues limited his ability to bounce back after outings and wouldn’t allow him to pitch on back-to-back days early in the season. Zych fills the spot in the bullpen vacated by right-hander Drew Storen, who was placed on the DL with shoulder inflammation on Monday.

“It took a lot longer than I thought,” Zych said of his recovery. “It was weird. I don’t really know how to explain it. It was just uncomfortable for a while. I was finally able to push through it (in Arizona).”