Chris Eubank Jr claimed the WBA's interim middleweight title after Matt Korobov suffered an early shoulder injury in Brooklyn.
Making his debut in the United States, British boxer Eubank (29-2) was declared winner by TKO in the second round on Saturday.
Russian Korobov (28-3) appeared to hurt his shoulder 20 seconds into the second round and referee Steve Willis eventually stopped the fight at Barclays Center.
"I feel like I was just about to get my swagger on," Eubank, who was back in action for the first time since beating James DeGale in February, said. "I hit him with a shot, and he turned around and stopped.
"I was about to go at him, but the referee told us to stop. I guess something happened with his shoulder, I don't know.
"There's nothing to take from the fight, I threw like three or four punches. I was just warming up.
"Karma is a real thing, whatever he's done, I don't know, there's a reason whatever happened, happened.
"This wasn't my dream debut here, I wanted to get my knockout and excite the fans."