Star LSU linebacker Harold Perkins left the field in the fourth quarter of the Tigers’ win over UCLA on Saturday after delivering a violent blow to a receiver sprinting down the middle of the field.

According to the ABC broadcast crew, Perkins was ruled out with a knee injury. After being examined in the LSU medical tent, he slowly walked to the locker room under his own power.

“We’ll be doing all the diagnostic testing tonight and tomorrow,” coach Brian Kelly said. “We’ll be able to give you a better answer at our press conference on Monday.”

Last week in the win over South Carolina, LSU used Perkins at strongside linebacker and began experimenting with a 4-3 defense. The same formation was adopted in Saturday’s game against UCLA, a game in which the Tigers struggled to stop the Bruins’ offense in the first half but held them off in the second.

After Perkins left the game, safety Jardin Gilbert stopped a UCLA attack with an interception, giving the LSU offense a chance to extend its 31-17 lead.

“We can still stay with our Buffalo package,” Kelly said. “We can go back to our dime package and drop Major (Burns). So we have a lot of options. We hope he’s OK. We hope he comes back to us. But we’ll be able to move into other packages that are similar to what we’re doing.”