Light heavyweight prospect Marcus Browne stopped former title challenger Thomas Williams Jr. in Round 6 of their scheduled 10-round bout on the Adrian Broner-Adrien Granados undercard on Saturday in Cincinnati, Ohio.

Browne (19-0, 14 knockouts), a 26-year-old southpaw from Staton Island, New York, was in command from start to finish, dropping Williams in Rounds 2, 4 and 6, but the 2012 U.S. Olympian flirted with disqualification in the second stanza when he landed an illegal punch after dropping his 29-year-old opponent with a jab.

Williams (20-3, 14 KOs), a scrappy southpaw from Ft. Washington, Maryland who has been in his share of shootouts, had the look of a shopworn fighter throughout the bout. His legs did not appear to be under him, especially when Browne felled him to one knee with a jab. Browne then stepped in and landed a left hand to the back area of Williams’ head while his opponent had one knee and one glove on the canvas.

Referee Ken Miliner correctly called the knockdown, then penalized Browne a point for the illegal punch, and then gave Williams up to five minutes to recover from the foul. Williams took about three minutes and the round resumed. He was stunned by a hook before the round ended, and wasn’t able to get his offense going in subsequent rounds. The fight was stopped after the third knockdown when Miliner counted Williams out 42 seconds into Round 6, but it could have been halted anytime after Round 4.

Browne told Showtime’s Jim Grey that he thought Williams was in a “squatting position” and not down when he nailed him with his left cross. Browne then called bout WBC light heavyweight titleholder Adonis Stevenson, who knocked out Williams in four rounds in Williams’ last bout last July.

Browne, who exhibited sharp stick-and-move technique while boxing Williams from a distance, may last a bit longer than Williams did against Stevenson.