A knee injury will remove Stephan Bonnar (Pictures) from April 2 clash with Matt Hamill (Pictures), and sideline the TUF alum for at least six months.

The popular Bonnar sustained a complete tear of the lateral collateral ligament in his left knee while training in Las Vegas, Yahoo!'s Kevin Iole reported Monday. The injury will require surgery, and a timetable for Bonnar's return offers a six-month recovery time.

Bonnar, 30, returned to action in July from a nine-month suspension after testing positive for anabolic steroids following his Aug. 2006 rematch with Forrest Griffin (Pictures). Bonnar easily won his return bout against Mike Nickels (Pictures), before taking a second round stoppage over Eric Schafer (Pictures) in October.

No replacement opponent has yet been confirmed for Hamill. The Bonnar-Hamill bout was scheduled to be part of the live Spike TV telecast of the UFC's April 2 card from Broomfield, Colo.