Usman and Masvidal, who have been linked as potential future opponents, ran into one another between radio interviews. Usman provoked Masvidal, saying "do something" repeatedly.
The two have exchanged trash talk on social media and in the press, but this is the first time they have crossed paths directly since a possible bout gained traction.
"You're talking tough," Usman said.
Masvidal pointed to the cast on Usman's left hand. Usman is currently dealing with a thumb injury stemming from his UFC 245 win over Colby Covington last month.
"You got a cast on, b----," Masvidal said. "You lucky. That's the only reason why nothing is happening."
Masvidal is thought to be the top contender for Usman's title. While Conor McGregor has been talked about as a possible foe for the red-hot Masvidal, UFC president Dana White said after UFC 246 on Jan. 18 that he'd prefer McGregor fight lightweight champion Khabib Nurmagomedov next, while Masvidal faces Usman.
Usman (16-1) has won 11 straight in the UFC and is ESPN's No. 8-ranked pound-for-pound fighter. Masvidal (35-13) won the mythical BMF title by beating Nate Diaz at UFC 244 in November and is ESPN's No. 2-ranked welterweight.