With opponent T.J. Dillashaw (9-2 MMA, 5-2 UFC) promoted to a headlining spot, his original opponent, Takeya Mizugaki (19-7-2 MMA, 6-2 UFC), now has a new matchup, as well.

Bantamweight Francisco Rivera (10-2 MMA, 3-1 UFC) has stepped in to fight Mizugaki, UFC officials today told MMAjunkie.

After UFC 173 lost a planned headliner between Chris Weidman and Lyoto Machida, Dillashaw was booked to fight bantamweight champion Renan Barao (32-1 MMA, 7-0 UFC) in the event’s new championship main event. MMAjunkie first reported the fight on Thursday.

UFC 173 takes place May 24 at MGM Grand Garden Arena in Las Vegas. The main card, including Barao vs. Dillashaw and Mizugaki vs. Rivera, airs on pay-per-view following prelims on FOX Sports 1 and UFC Fight Pass.

Mizugaki is ranked No. 12 in the USA TODAY Sports/MMAjunkie MMA bantamweight rankings. Rivera is an honorable mention.

Mizugaki, a former WEC title challenger, has won four straight fights, all by decision. The 30-year-old Japanese fighter’s recent wins have come over the likes of Nam Phan, Erik Perez and Bryan Caraway. He hasn’t lost a bout in more than two years, when Chris Cariaso beat him via decision at UFC 144.

Rivera, meanwhile, is 3-0 (with one no-contest) since returning to the UFC for a second stint. Although Reuben Duran choked him out at the TUF 13 Finale in 2011, the 32-year-old Californian in undefeated since then with two wins at Tachi Palace Fights and his current winning streak with the UFC, which includes back-to-back TKO wins over Edwin Figueroa and George Roop.

The full UFC 173 card now includes:

MAIN CARD (Pay-per-view, 10 p.m. ET)

Champ Renan Barao vs. T.J. Dillashaw – for UFC bantamweight title

Junior dos Santos vs. Stipe Miocic

Takeya Mizugaki vs. Francisco Rivera

Tony Ferguson vs. Katsunori Kikuno

James Krause vs. Jamie Varner

PRELIMINARY CARD (FOX Sports 1, 8 p.m. ET)

Michael Chiesa vs. Francisco Trinaldo

Chris Holdsworth vs. Kyung Ho Kang

Mitch Clarke vs. Al Iaquinta

Anthony Njokuani vs. Vinc Pichel

PRELIMINARY CARD (UFC Fight Pass, 6:30 p.m. ET)

Yves Edwards vs. Piotr Hallmann

Doo Ho Choi vs. Sam Sicilia

Jingliang Li vs. Danny Mitchell

For more on UFC 173, stay tuned to the UFC Rumors section of the site.

(Pictured: Francisco Rivera)