Cook tore his anterior cruciate ligament in his left knee, which will require reconstructive surgery. The normal recovery time for a torn ACL would extend well into the season.
"I'm extremely disappointed for Tommy, and also for our team," Brooks said.
As a junior, the Victoria, Texas native caught 21 passes for 222 yards and a touchdown. He was projected to start opposite Keenan Burton at the starting wide receiver spots.
"It is difficult to lose the experienced leadership that Tommy brings to our team. I have encouraged Tommy, and he has agreed, to be with the team next season and help develop our young receivers."
The athletic department could seek a medical hardship case on behalf of Tommy Cook, if the senior wide-out wishes to join the team for a sixth season.