Interim heavyweight champion Frank Mir sustained a knee injury while training for his upcoming fight against Brock Lesnar at UFC 98: "Lesnar vs. Mir 2" from the MGM Grand Garden Arena in Las Vegas, Nevada, on May 23 and has been forced out of the main event.

Mir will require time to heal after recently undergoing minor knee surgery to repair the damage. He is expected to make a full recovery. There is no timetable for a return; however, the good news is that it could be as soon as this summer.

Therefore, the highly anticipated heavyweight title unification match appears to be temporarily on hold -- not canceled -- for now.

More from MMAmania.com on this breaking news in a bit.