Two of Bellator's biggest rivals will finally get a chance to settle their differences later this year.

Featherweight champion Patricio "Pitbull" Freire will move up to 155 pounds to challenge lightweight champion Michael Chandler at Bellator 221 on May 11 at Allstate Arena in Rosemont, Illinois, multiple sources told ESPN. The promotion is expected to formally announce the grudge match later this week, sources said.

Michael Chandler, right, knocked out Patricky Freire at Bellator 157 in 2016. Now, Patricky's brother, Patricio, wants to avenge his brother's defeat when he faces Chandler at Bellator 221 in May. Dave Mandel/Sherdog.com.

This will mark Bellator's second champion-versus-champion fight in less than a year. In September, welterweight champion Rory MacDonald moved up to 185 pounds to challenge middleweight king Gegard Mousasi. MacDonald ultimately lost in his bid to become Bellator's first double champ.

Last month, light heavyweight champion Ryan Bader became Bellator's first double champion when he knocked out Fedor Emelianenko to claim the vacant heavyweight title at Bellator 214. The UFC, by comparison, has had three double champions in its history.

Chandler and Freire have been entangled in a war of words for almost three years. Their feud seemed to reach a fever pitch when Chandler knocked out Freire's older brother, Patricky, in June 2016. After the win, Freire got in Chandler's face during his celebration atop the cage and seemingly called him out. Since then the two have gone back and forth on social media and via the press, but the fight was never put together for various reasons. They will finally get to fight it out later this year, with Chandler's lightweight title on the line.

Chandler (19-4) regained the title in December with a decision victory over Brent Primus, while Freire (28-4) most recently defended the featherweight title in November with a decision win over Emmanuel Sanchez.

Also slated for that card is the return of former WWE star Jake Hager (aka Jack Swagger), according to sources. Hager was successful in his MMA debut last month and is getting right back to work, though his opponent has not been finalized yet, sources said.

In addition, the event is expected to feature former 170-pound champion Douglas Lima vs. the winner of this weekend's Paul Daley vs. Michael Page welterweight tournament fight and undefeated rising star A.J. McKee versus former featherweight champion Pat Curran.