SEATTLE -- Veteran right-hander Felix Hernandez will likely be sidelined 4-6 weeks, according to Mariners manager Scott Servais, after an MRI exam revealed a Grade 1 strain of the lat muscle behind his right shoulder.

Hernandez said he felt pain in the shoulder on his final pitch on Friday, when he was removed after 2 1/3 innings in Boston having allowed six hits on seven runs and three walks in a 9-5 loss.

The 33-year-old is 1-4 with a 6.52 ERA in eight starts this season and 1-11 with a 6.41 ERA in 19 games (18 starts) since July 6. He showed signs of improvement in several outings this year, but struggled in his past three while allowing 17 earned runs and 22 hits in 13 1/3 innings.

The six-time American League All-Star and 2010 AL Cy Young Award winner is in the final year of a contract paying him $27 million for this season.

Servais said left-hander Wade LeBlanc will likely come off the 10-day injured list at some point this weekend against the Twins to take Hernandez’s rotation spot. LeBlanc threw 4 1/3 innings in a Minor League rehab outing for Triple-A Tacoma on Monday and could be ready to rejoin the rotation by Saturday if kept on typical four days' rest.

With an off-day on Wednesday, Marco Gonzales could be bumped up to pitch in Hernandez’s turn on Friday and remain on his normal schedule as well, though no decision has been announced on the Twins series beyond rookie Erik Swanson throwing in Thursday’s opener.

Hernandez was only on the injured list twice in the first 11 years of his 15-year career with the Mariners -- with a strained right elbow in 2007 and sprained left ankle in ’08 -- but this is his fifth time sidelined by injury since '16.

He missed nearly three months with a right calf strain in '16, three months spread over two different stints on the shelf with right shoulder inflammation in ’17 and 12 days last year with lower back stiffness.

“It’ll be ice and rest and a lot of exercises,” Hernandez said. “I’m not a big fan of the DL, or IL now. I didn’t have any [injuries] for a long time.”

Hernandez said he didn’t feel any problem with the shoulder until his last batter in Fenway.

“I threw that pitch and just felt something there,” he said. “I didn’t realize what it was because I’ve never had a lat problem. I just have to keep working and get healthy again.”

Hernandez said he won’t be able to throw at all for a week or two, but doesn’t believe the issue should sideline him too long. Mariners closer Hunter Strickland suffered a more severe Grade 2 lat strain six weeks ago and is just now starting to play catch and begin building back up for a possible midseason return.

“The initial time frame I was given was a 4-6 weeks situation,” Servais said. “It’s not as severe as what Hunter Strickland had. Hopefully it’s not quite that whole period, but it’s disappointing for him.”

LeBlanc’s impending return will help fill the gap. The veteran southpaw went 2-0 with a 4.50 before straining his right oblique in his third start of the season. He said Monday’s outing served him well.

“It felt good to be back out there,” LeBlanc said. “I was a little rusty on some pitches here or there, but the main thing I was looking for was being able to make adjustments. You’re going to make mistakes even if you’re on start No. 20 in your prime. It’s the ability to make the adjustment on the next pitch and get back where you need to be and I was able to do that. So it was a good step.”

LeBlanc said he threw 60 pitches in the Las Vegas start, had no issues at all with the oblique and will be prepared to go whenever the Mariners give him the green light.

“As soon as I was ready, I knew there’d be a spot for me,” he said. “Unfortunately it happens to come at a time when Felix goes down. He’s a big part of the rotation. All five guys are a big part of the rotation. You need everybody.”

Worth noting

• Kyle Seager went 1-for-4 with a single and walk in his first rehab outing at designated hitter for Triple-A Tacoma on Tuesday and will play third base on Wednesday for the Rainiers in Las Vegas as he sees his first action since surgery to repair a torn tendon in his left hand in Spring Training. Seager is expected to be ready to come off the 60-day injury list as soon as he’s eligible on May 25.

• Dee Gordon was out of the lineup for a fifth straight day on Tuesday due to a bruised right wrist, but he took part in pregame fielding work and batting practice. Gordon said the wrist was close to 100 percent, and Servais is hopeful the veteran second baseman will be ready to start on Thursday against the Twins after Wednesday’s off-day.

• The Mariners haven’t received any further clarification on the rules enforcement against Cory Gearrin’s “toe tap” in his delivery that came into play in Monday’s game, but Servais said the veteran right-hander will need to adjust going forward.

“Cory’s whole delivery and his whole tempo is unique,” Servais said. “It is a slower pace. But the toe tap is kind of a big thing just because it’s his reminder to stay back over the rubber. You’ll see other guys do a similar type thing -– Kenley Jansen, Clayton Kershaw -– they just don’t quite touch the ground. But Cory was actually touching the ground, and that’s illegal to do. He now knows that and will make adjustments.”