The UFC announced Saturday that veteran middleweight Chris Camozzi has re-signed with the promotion and will rematch Souza on just seven days' notice at the April 18 event.
Souza (21-3, 1 NC) was initially slated to fight fellow top-ranked middleweight Yoel Romero, however Romero withdrew after sustaining a knee injury this week in training.
Camozzi (21-9) has notched back-to-back first-round finishes since being cut from the UFC in late-2014. The former TUF 11 product fought to a 7-6 record over 13 UFC contests in his first run with the promotion, including a memorable May 2013 loss that saw Souza put Camozzi to sleep in less than four minutes with arm-triangle choke.
"The important (thing) now is to keep Jacare active and fighting," Souza's manager Gilberto Faria told MMAFighting.com's Guilherme Cruz.
"He hasn't fought in six months and it wouldn't be good to wait more four or five months. We're going to war, we're going to fight. It's another day in the office. We will fight, bring the win and make some money. We hope the next fight is going to be a big one to put Jacare in a higher level. The important (thing) now is to fight.
"Jacare has the obligation to win because it's a rematch and he won the first fight," Faria added. "We wanted Bisping as the replacement and even though Bisping was ready to fight a week later he didn't want to take the fight. Fighting Camozzi doesn't add anything to Jacare's career, but it's good that he can stay active and do everything he trained to do."
UFC on FOX 15 takes place at the Prudential Center in Newark, New Jersey. An updated UFC on FOX 15 fight card can be seen below.
Main Card (FOX, 8 p.m. ET)
Lyoto Machida vs. Luke Rockhold
Chris Camozzi vs. Ronaldo Souza
Max Holloway vs. Cub Swanson
Felice Herrig vs. Paige VanZant
Preliminary Card (FOX Sports 1, 6 p.m. ET)
Beneil Dariush vs. Jim Miller
Patrick Cummins vs. Ovince Saint Preux
Corey Anderson vs. Gian Villante
Aljamain Sterling vs. Takeya Mizugaki
Preliminary Card (UFC Fight Pass, 4:15 p.m. ET)
Tim Means vs. George Sullivan
Diego Brandao vs. Jimy Hettes
Chris Dempsey vs. Eddie Gordon