The Mariners’ starting rotation took two steps forward Wednesday and one step back.

Starting pitcher James Paxton was placed on the 15-day disabled list after MRI results earlier in the day revealed he had a strained lat muscle. Paxton was injured in the sixth inning of Tuesday’s home opener and had to leave the game. He had retired 14 straight batters after a rocky start.

Paxton said he and the Mariners are still in the “assessment stage,” and while he didn’t think the injury was anything other than a strained lat, he said the club would re-evaluate the severity of the injury after 15 days.

Paxton, 25, is 2-0 with a 2.25 earned-run average in two starts this season.

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“I was feeling good out there,” Paxton said. “Not the ideal situation, but I’m just going to deal with it and get ready to go.”

Manager Lloyd McClendon said Chris Young would start Sunday in Paxton’s place. The Mariners also recalled reliever Lucas Luetge to the 25-man roster.

Meanwhile, two other starters who are projected to contribute in big ways this season inched closer to returning.

Hisashi Iwakuma threw off a mound for the first time since straining a ligament in his middle finger in February, and Taijuan Walker made his second minor-league rehab start at Class AA Jackson. It’s possible both could return by the end of the month.

Iwakuma, an All-Star last year, said he felt good and experienced no pain in his finger. He threw 34 pitches, mostly fastballs.

“I just wanted to get that feel back,” Iwakuma said.

He will throw off a mound again Saturday and will mix in curveballs and sliders. He will also throw more pitches to begin building up arm strength.

Iwakuma didn’t know when he might begin a rehab assignment and didn’t have a time frame for returning.

“Hopefully he’ll continue to move forward,” McClendon said.

Walker, 21, is recovering from shoulder soreness he experienced in March. He made his first rehab start for Class A High Desert last week and struck out seven hitters in 41
3 innings.

He put up even more dazzling numbers in his second start, when he struck out 10 batters in five innings for Jackson. He threw 84 pitches and gave up just three hits.

“I feel like I’m ready now, but that’s not up to me,” Walker said. “My arm’s been feeling really good.”

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