TJ Waldburger has been forced to pull out of his UFC 161 fight against Sean Pierson and replacing Waldburger in the bout will be Kenny Robertson. 
UFC officials announced the changed on Thursday night and there was no reason given on why Waldburger pulled out of the fight.
UFC 161 takes place on June 15th from the MTS Centre in Winnipeg and will be headlined by Renan Barao defending the UFC interim bantamweight title against Eddie Wineland.
Pierson (13-6) was signed by the UFC in 2010 and won his debut at UFC 124 against Matthew Riddle. After that win, he dropped back to back fights and is currently on a two fight winning streak with the most recent win coming at UFC 152 against Lance Benoist.
Robertson (12-2) is in his second stint in the UFC and has gone 1-1 since returning to the organization. After losing to Aaron Simpson in his return fight to the UFC last year, he defeated Brock Jardine at UFC 157 earlier this year and won the submission of the night bonus.
The current UFC 161 card is below:
Renan Barao (32-1, 1NC) vs. Eddie Wineland (20-8-1)
Antonio Rogerio Nogueira (21-5) vs. Mauricio “Shogun” Rua (21-7)
Dan Henderson (29-9) vs. Rashad Evans (22-3-1)
Alexis Davis (11-5) vs. Rosi Sexton (13-2)
Stipe Miocic (9-1) vs. Soa Palelei (18-3)
Pat Barry (8-5) vs. Shawn Jordan (14-4)
Jake Shields (27-6-1, 1NC) vs. Tyron Woodley (11-1)
Roland Delorme (8-1, 1NC) vs. Edwin Figueroa (9-2)
Ryan Jimmo (17-2) vs. Igor Pokrajac (25-9, 1NC)
Sean Pierson (13-6) vs. Kenny Robertson (12-3)
Yves Jabouin (18-8) vs. Dustin Pague (11-8)
Sam Stout (20-8-1) vs. Isaac Vallie-Flagg (14-3-1)
Mitch Clarke (9-2) vs. John Maguire (18-5)