Per 247Sports.com, Blacklock’s suffered the injury during a non-contract drill on Tuesday.
A posting on one of the 6-foot-4, 329-pound sophomore’s social media accounts showed him at an orthopedist’s office.
Blacklock registered 27 tackles and two sacks en route to being named the co-Big 12 Defensive Freshman of the Year along with Oklahoma linebacker Kenneth Murray.
With Blacklock out, the Horned Frogs are expected to turn to redshirt freshman Terrell Cooper for additional playing time.
TCU opens the season Sept. 1 against Southern University.