LSU and pitcher Eric Walker received the worst possible news Thursday when they found out Walker will need Tommy John surgery, requiring him to miss the 2018 season.

Walker will have the surgery next Wednesday near his Arlington, Texas, home. It will be performed by Keith Meister, the head physician of the Texas Rangers.

The typical recovery time for Tommy John surgery is 12-16 months.

“Eric is an amazing young man,” LSU coach Paul Mainieri said. “He’s very composed and poised. He just kind of took the attitude of, ‘OK; if these are the cards that are dealt to me, now I’ve got to get myself mentally prepared and go through it.’

“In his words, he went through the ‘mourning phase.’ Now he realizes he’s just got to get it done, and it’s going to be a long road back, but he’s going to take that challenge on.”

LSU now must replace its entire weekend rotation in, as Walker was set to be the only returning member.

It will be the third time in Mainieri’s tenure his team had to replace the entire weekend rotation, and the results were mixed: He did so in 2009, when his team won the national championship, and again in 2011, when it missed the NCAA tournament.

“Before the (2017 season), I said we were bound and determined to develop a third starter because we didn’t want to go into 2018 without any proven returning starters,” Mainieri said. “As it turns out, these are the cards that were dealt to us, and we’re going to have to do the best we can.”

Among candidates to fill out the rotation next season are Zack Hess and Caleb Gilbert, both of whom performed well in limited starting roles this season, though Hess was at his best out of the bullpen.

LSU will also bring in 11 new pitchers this fall from the high school and junior college ranks.

“It’s going to make for a busy fall for Alan Dunn,” Mainieri said. "But he’ll work his magic with those guys. We’ll come up with somebody.”

Mainieri declined to say whether Walker fully tore the ulnar collateral ligament in his right elbow, but he said the damage was significant enough to have two physicians recommend the surgery.

Walker first met with the LSU team doctor after the Tigers returned from Omaha, Nebraska, then sought a second opinion from Meister in Arlington.

“Both doctors said the same thing, evaluated it the same way and recommended the surgery,” Mainieri said.

Walker removed himself from the College World Series four pitches into the third inning of his final start, against Oregon State, after feeling discomfort in his right forearm.

He initially felt that discomfort during a simulated game before LSU traveled to Omaha for the College World Series, but the feeling subsided and he went through a subsequent bullpen session with no ill effect, leading Mainieri and the LSU training staff to believe it was a muscular strain.

But the day after Walker’s Oregon State outing, the pain radiated toward his elbow, causing Mainieri to shut down Walker for the season.

Walker turned in a fantastic freshman season, earning several Freshman All-America honors after going 8-2 with a 3.48 ERA.

He was at his best down the stretch. Walker was the winning pitcher in the Southeastern Conference tournament championship, shutting down Arkansas for 7.2 innings, and he pitched into the ninth inning of LSU’s NCAA regional championship game against Rice.

Walker became the second LSU pitcher this season to require the surgery. Reliever Doug Norman had his operation in March after tearing his ulnar collateral ligament Feb. 26.

Mainieri said words of encouragement have been pouring in for Walker.

“I’ve had text messages from people like (former LSU pitcher) Nick Goody, who had to have surgery on his arm a couple years into pro ball and now he’s pitching in the big leagues,” Mainieri said. “The more he hears that from people, the more inspired and motivated he’ll be to get through the tough rehabilitation and return to his normal form.”

Follow Luke Johnson on Twitter, @ByLukeJohnson.