The UFC, the world's biggest mixed martial arts promotion, signed top-level lightweight Eddie Alvarez to an exclusive contract on Tuesday.  

The 30-year-old Philadelphia native will make his debut in the octagon against Donald "Cowboy" Cerrone in the co-main event at UFC 178, which will be held in Las Vegas on Sept. 27, according to UFC.com.

Cerrone was originally supposed to fight Bobby Green at the event, but Green will instead fight in November against an opponent that has not yet been determined.

The signing took place not even 12 hours after Alvarez was released from Bellator MMA while he was the promotion's lightweight champion, Bloody Elbow reported.

Alvarez currently holds a 25-3 record in MMA, which includes knockout victories over Shinya Aoki and Patricky Freire.

Debuting in Bellator in 2009, Alvarez achieved a 9-1 record in the promotion and became its lightweight champion, UFC reported. While Alvarez also holds victories over Toby Imada, Josh Neer, and Roger Huerta, his most memorable accomplishment in the company was avenging his 2011 loss to Michael Chandler, beating Chandler in November 2013 to regain his title in a split decision.

Before being put against Green, Cerrone was supposed to fight Khabib Nurmagomedov at UFC 178, but Nurmagomedov blew out his knee just minutes after the contract signing, Bloody Elbow reported. Green was also scheduled to fight Jorge Masvidal before replacing Nurmadomedov. Cerrone (24-6, 1 NC) has won all three of his fights this year, defeating Adriano Martins, Edson Barboza and Jim Miller.

Other fights scheduled for UFC 178 include a featherweight bout between Dustin Poirier and Conor McGregor, Tim Kennedy taking on Yoel Romero, and flyweight champion Demetrious Johnson defending his title against Chris Cariaso.