The school confirmed Wednesday that Mettenberger will miss the Tigers' bowl game but did not disclose specifics about the injury, per school policy.
"We are very disappointed for Zach," coach Les Miles said Wednesday. "He's been a tremendous leader for our team and he's as competitive a guy as I have ever been around. He's had a great impact on our program."
Mettenberger was hit on his left knee during the fourth quarter by Arkansas defensive tackle Byran Jones. The senior quarterback was wearing a brace on the knee as a precautionary measure, but the force of the blow bent his knee back, causing the damage.
A source said that once the sprain heals -- in an estimated two weeks -- Mettenberger would have surgery to repair his ACL.
Mettenberger, who is known for his arm strength, was thought to be no worse than a mid-first-round pick in the 2014 NFL draft before he suffered the injury, two high-ranking league personnel sources said.
"I know Zach will work extremely hard to rehabilitate his knee and I don't anticipate this injury having any impact on what should be a great future in the NFL," Miles said.
Backup quarterback Anthony Jennings, who took over for Mettenberger against the Razorbacks and led LSU (9-3, 5-3 SEC) to victory late in the game, will be the starter for the team's bowl.
Mettenberger could be able to throw at LSU's pro day (likely in March), assuming no further issues come up during the ACL surgery, according to sources in the scouting community.
Mettenberger threw for 3,082 yards and 22 touchdowns this season and had a 64.9 completion percentage, all of which rank third all time at LSU. He finished his career with a 19-6 record as a starter and became the third quarterback in LSU history to throw for 2,500 or more yards in back-to-back seasons.
Adam Caplan is an ESPN NFL Insider.