Jarrett Hurd retained his IBF and WBA light-middleweight titles with a stoppage win over Jason Welborn in Los Angeles.
In the chief support act ahead of Deontay Wilder's defence of the WBC heavyweight belt against Tyson Fury, the unbeaten Hurd recorded a 23rd straight victory courtesy of a sickening body shot in the fourth round.
However, the American did not have it all his own way, Welborn standing his ground against the champion as he enjoyed moments of success.
Hurd himself looked in trouble early in the fourth, getting stuck on the ropes as the challenger unloaded on him, but turned the tide to force the stoppage before the bell sounded.
The final shot was a wicked right hand that dropped Welborn, the former British champion unable to rise in time to beat the count.
A clash with Jermell Charlo looks to be on the horizon for Hurd in 2019, with the pair sharing a heated verbal exchange in the ring during the post-fight interview on Showtime.
Also in action, Luis Ortiz - who lost to Wilder in March - won inside the distance, eventually putting away Travis Kauffman in the 10th round of a non-title bout.
The Cuban was comfortably the better of the two big men, dropping his rival three times in total to record a second victory since falling short in his bid to capture the WBC title earlier in the year.
Also at heavyweight, British prospect Joe Joyce wasted little time in recording a victory over Joe Hanks.
Joyce stopped his opponent inside the opening round, a big left hook ending the contest quickly as he extended his record to 7-0 as a professional.