SEATTLE -- Mariners left-hander Wade LeBlanc is expected to miss about four to six weeks with a Grade 2 strain of his right oblique muscle, manager Scott Servais said on Sunday, as rookie right-hander Erik Swanson was recalled from Triple-A Tacoma to take his spot.

Swanson, the Mariners’ No. 9 prospect per MLB Pipeline, pitched two innings in relief in his Major League debut on Thursday before being optioned back to Tacoma. He’ll be available to pitch out of the bullpen initially, but he is expected to take LeBlanc’s spot in the rotation on Wednesday afternoon against the Indians.

“Obviously you don’t want to see anybody go down, but I’m definitely happy to be back up here,” Swanson said. “Getting that first one under my belt was really good.”

LeBlanc was placed on the 10-day injured list for a team that has already lost third baseman Kyle Seager and closer Hunter Strickland.

Reliever Shawn Armstrong missed about a month with a Grade 1 strain of his left oblique before returning last week, so the Mariners are hopeful LeBlanc won’t be out too long.

“We’ll see how he progresses and heals up, but I’d hope within three weeks, or whatever, he’d begin tossing a ball,” Servais said. “Wade is a little different building him up. He’s usually in the 80- to 90-pitch range anyway.

“I’m sure at some point he’ll have to do a rehab assignment and see where we’re at from there. But that’s a long way from now. We have a lot of season left to play. Guys get all frustrated and I show them the calendar. We have a lot of ballgames left to go. We’ll get him back.”

LeBlanc was pulled from Friday’s start against the Astros after getting two outs in the fifth inning, holding a 3-2 lead at the time. The 34-year-old is 2-0 with a 4.50 ERA in three starts this year and 11-5 with a 3.79 ERA in 178 innings over 35 games (30 starts) since re-signing with Seattle last year.

The 11-year veteran has been a journeyman most of his career, but he finally found some longer security with a unique deal last year that pays him $2 million this season, with a $5 million team option for each of the next three years that becomes guaranteed if he pitches 160 innings the previous year.

Swanson pitched better than his line showed in his debut in Seattle’s 7-6, 10-inning win on Thursday at Kansas City, allowing two runs in two innings while striking out four. The 25-year-old likely wouldn’t have allowed any runs if not for a pop fly that fell in for a double on the windy afternoon at Kauffman Stadium, which opened the door for two more hits in his first inning of work.

“Obviously the outcome wasn’t what I wanted, but that’s part of it,” Swanson said. “I was happy with it. Moving forward, getting that first one under my belt is a good confidence booster for sure.”

The youngster flashed a 95-mph fastball and good poise under difficult circumstances, and he now figures to earn his first MLB start on Wednesday in the finale of the upcoming three-game series with the Indians.

“He’s got a good fastball, with some riding action on it,” Servais said. “He got a lot of swings and misses on it. He’s a young pitcher and has things to work on, but he had a really good outing in Spring Training against the Dodgers that stood out and I thought he threw the ball well in Kansas City the other day."

Swanson threw five scoreless innings in his only appearance with Tacoma, allowing six hits and no walks while striking out eight on the Rainiers’ Opening Day. He was one of three top prospects acquired from the Yankees during the offseason in the trade for James Paxton.