All four Bellator champions will be competing in non-title super fights until their title challengers are determined. One previously announced super fight was lightweight champion Eddie Alvarez taking on Josh Neer.
Soto (8-0) put his name on the map last season for his wins over Ben Greer, Yahir Reyes and tournament favorite Wilson Reis to capture the featherweight strap. During Bellator's off-season, Soto finished Mike Christensen with a gogoplata at Tachi Palace Fights in October.
After three straight losses in the UFC in 2007, Saraiva returned to the local cards in California and Georgia and has won eight of his last 10 fights. According to Bellator, Saraiva is unbeaten in six fights as a featherweight.
"This is a great matchup between two extremely tough fighters -- one who's on his way up and one who's in the midst of a great comeback," Bellator CEO Bjorn Rebney said in a statement. "Diego will be a great test for Joe as he prepares to defend his belt later this year."