Chris Weidman injured, out of UFC 173 match with Lyoto Machida

The champ is on the shelf.

Josh Hedges/Zuffa LLC/Zuffa LLC via Getty Images

First, the challenger was out of the Memorial Day weekend title matchup. Now, the champion is out, too.

UFC middleweight kingpin Chris Weidman has been forced to withdraw from his first post-Anderson Silva defense, scrapping the proposed UFC 173 main event, FOX Sports has learned.

Two sources with knowledge of the situation confirmed that Weidman would not be able to fight as the result of a minor knee injury that will require surgery. 

The UFC corroborated the information in a follow-up text to FOX Sports, and said that his match against Lyoto Machida will be moved to UFC 175 on July 5.

One of the sources told FOX Sports that on Monday, Weidman saw a doctor that affirmed an original prognosis that ruled him out of the May 24 matchup in Las Vegas.

The 29-year-old New Yorker won the title from Silva in July 2013 with a second-round knockout, and had his first successful defense five months later when Silva broke his leg on a kick during the second round of their rematch. He remains undefeated at 11-0.

Weidman was originally supposed to face No. 1 contender Vitor Belfort at UFC 173, but after Nevada passed a ban of the controversial testosterone replacement therapy, Belfort, who had previously had a therapeutic usage exemption for the treatment, was pulled out of the fight.

Machida has won both of his middleweight starts since dropping from light-heavyweight, with an impressive knockout of Mark Munoz followed by a unanimous decision over Gegard Mousasi.

With Weidman out, the hunt is on for a new UFC 173 headliner.