TACOMA — The Mariners could be adding a hard-throwing left-hander to their starting rotation right around the trade deadline.

No, not that lefty from Tampa Bay. It’s one of their own: James Paxton.

On Tuesday at Cheney Stadium, Paxton took another major step in returning to Seattle’s rotation, making the second start of his current rehabilitation stint.

Paxton threw three innings, giving up three runs (two earned) on three hits, including two homers, with four strikeouts and a walk in the Class AAA Tacoma Rainiers’ 4-0 loss to Las Vegas in the opener of a doubleheader.

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“I felt good,” Paxton said. “No pain or anything. I still have a few things to do as far adjustments.”

His fastball touched 95 mph and was around 93-94 most of the time, but his command was a little off.

It was evident in the first inning when Matt Den Dekker led off the game with a solo homer to right field on an elevated 2-1 fastball. Later in the inning, Paxton gave up two-run homer to Wilmer Flores, on another 93 mph fastball on a 3-2 count.

“I just left them up and over the plate,” he said. “I was drifting a little toward first base and I wasn’t able to finish things. I left the ball a little up.”

Paxton allowed a single in the second and worked a 1-2-3 third. At 60 pitches, he was done for the night.

“The second and third felt a little bit better,” he said. “It’s coming along. I made good progress tonight.”

Results aside, Paxton felt no discomfort in his lat or shoulder — the two injuries that have kept him out since early April.

“Right now the most important thing is being healthy,” he said. “The second thing is starting to tighten things up and get that good feeling.”

Paxton will make at least one more rehab start.

Tacoma won the nightcap, 4-3.

Everett 6, Boise 0

Nate Tenbrink hit a grand slam in a six-run AquaSox fourth and Jeffeson Medina (1-4) and two relievers combined on a three-hitter.

Ryan Divish: 206-464-2373 or rdivish@seattletimes.com