Weidman (11-0) will require minor surgery after sustaining a knee injury in training. As a result, his title defense against Machida (21-4) has been moved to the main event of UFC 175, which takes place July 5, 2014 at the Mandalay Bay Events Center in Las Vegas, NV.
A replacement main event for UFC 173 is expected to be finalized in the coming days.
The announcement marks the second recent shift in the middleweight title picture, as Weidman was initially slated to fight Vitor Belfort on May 24, 2014 at UFC 173. Belfort, however, withdrew from the event following the Nevada State Athletic Commission's ban on testosterone replacement therapy in late February, and of this writing, his future remains shrouded in uncertainty.
With Belfort out of the picture, Machida wasted little time stepping up and accepting the opportunity. Riding a perfect 2-0 record since dropping down to 185 pounds, highlighted by victories over Mark Munoz and Gegard Mousasi, the former light heavyweight champ is currently the No. 2 ranked middleweight on the UFC's official rankings.
Weidman, of course, captured the belt by dethroning record-breaking former champion Anderson Silva with back-to-back second-round TKO stoppages in 2013.
UFC 173 is scheduled to take place at the MGM Grand Garden Arena in Las Vegas, NV. An updated fight card can been seen below.