Anthony Pettis' first title defense has been put on hold.
The UFC lightweight champion won't square off against Josh Thomson at UFC on FOX 9 on Dec. 14 because he has suffered a knee injury, according to a report on FOX Sports Live on Sunday night.
UFC on FOX 9 will now be headlined by the rematch between UFC flyweight champion Demetrious Johnson and Joseph Benavidez, according to FoxSports.com.
The Johnson vs. Benavidez 2 fight was supposed to be the main event for the TUF 18 Finale on Nov. 30.
It is unknown what's next for Thomson or how long Pettis will be out at this time.