PEORIA, Ariz. -- Mitch Haniger's difficult run of health issues hit another bump on Thursday, as the Mariners’ 2018 All-Star right fielder underwent his second surgery in the past month to deal with ongoing problems with his lower back.

Mariners general manager Jerry Dipoto clarified Friday morning that Haniger had a microdiscectomy, which is a small repair of a vertebra, and remains in a hospital in Los Angeles.

“We don’t have a timeline on his return,” Dipoto said. “He seems to be in pretty good spirits. We’re expecting him to be here in camp, but we don’t have a timeline for that either. Mitch works hard and nobody will be more attentive to the detail. We’ll assess as we go and then find out how long this is going to take.”

Haniger had sports hernia surgery in late January after feeling pain while ramping up his offseason hitting program in California. The 29-year-old hasn’t played since early June 2019 after rupturing a testicle on a foul ball. He attempted to come back from that injury several times last season, but he remained sidelined by pain in his back and core muscles.

“I think they’re all interconnected,” Dipoto said. “I’m not a doctor, but this didn’t come as a shock to our medical people that this was possible.”

Haniger was initially expected to miss at least six to eight weeks after the first surgery, but the Mariners aren’t making any predictions on when he might return at this point.

“It’s incredibly frustrating,” Dipoto said. “We all feel bad for him. It’s why we don’t really want to put a timeline on it because this has been a frustrating run for Mitch. There’s obviously been a lot of physical issues that have stemmed from one unfortunate incident. Hopefully, he’s able to get beyond it.”

With Haniger sidelined indefinitely, Seattle has rookies Jake Fraley and Braden Bishop contending for the starting role in right field, with fellow rookie Kyle Lewis already penciled into left field. Center fielder Mallex Smith is the only returning veteran, though the club has signed Carlos González to a Minor League deal with an invitation to big league camp.

Dipoto said Haniger’s second surgery doesn’t change that scenario.

“We didn’t anticipate he’d be here Opening Day regardless,” Dipoto said. “One of the things we’re doing organizationally is providing opportunities for young guys. I do think this opens up the door for increased opportunity for the Jake Fraleys and Braden Bishops of the world.

“There’s a reason we brought in a guy like CarGo, to provide some leadership and mentorship, and we’ll see how he looks physically when he gets into camp. We’re open to any possibilities, but we really don’t believe this is something that affects all of 2020. We have no timeline on it yet, but if this is an opportunity to provide the at-bats for the young guys, then that’s what we’ll do.”

Fraley, 24, figures as the early front-runner as the Mariners considered him one of their fastest-rising prospects last season after being acquired from the Rays. He struggled offensively in a brief showing in Seattle late in the season before spraining his right wrist and missing the final few weeks. But he's a strong defender who posted a .298/.365/.545 line with 19 homers, 80 RBIs and 22 stolen bases in 99 games with Double-A Arkansas and Triple-A Tacoma last year.

“All our guys in the Minor Leagues had good seasons. He had an incredible season,” manager Scott Servais said. “When he got to the big leagues, he was out of gas and struggled a little and then got hurt. He’s in a good frame of mind now and looks great. He’s added probably 15 pounds of really good strength, and I think he learned last year how important a really good routine is.”

Bishop, 26, is the other primary contender, though he’s bouncing back from his own physical issues last year after missing three months with a lacerated spleen. The Mariners also have two of MLB Pipeline’s top young outfield prospects in Jarred Kelenic and Julio Rodriguez. Both will be in Major League camp and receive long looks this spring, though at age 20 and 19 respectively, they’re expected to open the year in the Minors.

González, 34, is coming off a rough 2019 season in which he was released by both the Indians and Cubs, but the former Rockies standout is a three-time All-Star with a chance now to land a role if he’s healthy.