UFC lightweight champion Anthony Pettis stepped out of character on Twitter Wednesday afternoon, firing back at Nate Diaz and the comments the former contender made.

Diaz, who was moved into the main event of The Ultimate Fighter 18 Finale after Pettis was forced out of a December fight with Josh Thomson, asked why the UFC was paying him if he was always hurts.

Pettis, who suffered a knee injury, responded with “2 losses lissssp best offense is your middle finger = can’t talk shit!!!”

He later added to his account, “I shouldn’t let people who talk trash get me out of character,” with the hashtag, champ4areason.”

Pettis is still expected to face Thomson, likely in early 2014.