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LSU pitcher Caleb Gilbert (41) pats LSU starting pitcher Eric Walker (10) on the back as Walker leaves the game in the third inning during Game 6 of the College World Series between LSU and Oregon State, Monday, June 19, 2017, at TD Ameritrade Park in Omaha, Neb.

Advocate staff photo by HILARY SCHEINUK

OMAHA, Neb. — This is going to be tricky.

Not only must LSU navigate the losing side of its College World Series bracket, having to beat Florida State on Wednesday night just for the opportunity to try to take two in a row against a 56-4 Oregon State team, but it is going to have to do it short-handed.

Coach Paul Mainieri confirmed Tuesday that freshman right-hander Eric Walker’s season has ended after he experienced pain in his forearm that radiated into his elbow during his abbreviated start in Monday's 13-1 loss to the Beavers.

“When we get back home, we’ll take him to our orthopedic doctor, probably have an MRI done on his elbow and we’ll go from there,” Mainieri said. “The encouraging thing was he didn’t feel anything pop or anything like that. But the pain has radiated a little bit more than just that forearm, so obviously you’re concerned about the ligament.”

Beyond the obvious disadvantage of not having the steady and capable Walker on hand if LSU manages to force a winner-take-all game with Oregon State later this week, the Tigers must answer two questions.

The easier of the two questions: Who will take Walker’s spot in the rotation, if necessary?

The one that may be fraught with peril: Who will take the spot vacated by the guy starting in Walker’s place?

LSU’s pitching depth — at one point a strength, with three established and strong starting options, one go-to long relief option and two excellent late-relief options — is now cause for concern as it must win three straight games to advance to the championship round.

Mainieri answered the first question Tuesday: If LSU beats Florida State behind Jared Poché on Wednesday, then beats Oregon State behind Alex Lange on Friday, Caleb Gilbert would get the nod for the decisive game against the Beavers on Saturday.

“I think Caleb Gilbert would be a very capable replacement to get the ball on Saturday if we get that far,” Mainieri said.

Gilbert, a sophomore right-hander, has been one of LSU’s best pitchers during the stretch run. He went 4-0 with a minuscule 0.54 ERA in seven appearances during LSU’s 17-game winning streak, striking out 21 against just three walks in 16.2 innings.

Gilbert also had a strong appearance against the Beavers on Monday before his outing was derailed by an error that kept an inning alive, eventually leading to his departure after 2.2 innings.

Mainieri said he considered the possibility of saving Zack Hess for a starting role, but in order to even get to a Saturday showdown, LSU likely would have to use Hess in relief at some point.

“You’ve got to play nine innings,” Mainieri said. “If we get late in the game, we’ve got to have someone we can go to.”

LSU has confidence in Gilbert to pitch it into the championship series if it comes to that. The problem is that changing his role forces the Tigers to turn to someone else out of the bullpen if necessary, putting the onus on the starters to pitch deep into games.

“It takes everything for us to win at this point,” Mainieri said. “But first and foremost, your starting pitcher has to go out there and do a phenomenal job for us.”

Making things more challenging, usually steady fifth-year senior Hunter Newman has been shaky recently. Oregon State tagged Newman for five earned runs Monday, socking a grand slam off him to blow the game open in the sixth and then bringing home three more runs against him in the next inning.

“We’re going to need Hunter Newman to do much better than he did (Monday) night,” Mainieri said. “Hunter has been up and down for us a little bit, but he’s a fifth-year senior and he’s got to step up.”

“Step up” was a popular turn of phrase at practice Tuesday. With Walker out for the rest of the College World Series, others are either going to have to step up their production or step up into bigger roles.

“Obviously Eric has been a huge part of our team’s success this whole year,” Hess said. “It was tough seeing him go down (Monday) night — we’re hoping the best for him — but that means someone else is going to have to step up and perform.”

Poché looked back to earlier in the season, when setup man Doug Norman was lost for the year with a torn ligament in his elbow. LSU shifted Hess into that role, and he ended up thriving.

Do the Tigers have another Hess waiting in the wings? Probably not. But someone’s number will be called to fill the void created by Walker’s absence, and the Tigers expressed confidence it could be done.

“Obviously we wish we could have (Walker); he could’ve helped us out a lot,” Poché said. “But someone’s going to step up.”

Follow Luke Johnson on Twitter, @ByLukeJohnson.