NEW YORK – Vito Mielnicki Jr. accomplished something Saturday night that a proven veteran couldn’t do two months earlier.

The 20-year-old Mielnicki stopped Jimmy Williams in the sixth round of their eight-round junior middleweight match on the Danny Garcia-Jose Benavidez Jr. undercard at Barclays Center. Williams was still standing when referee Johnny Callas called an end to the action at 2:12 of the sixth round.

New Haven’s Williams (18-9-2, 6 KOs) went the distance with Milwaukee’s Luis Arias (20-3-1, 9 KOs, 1 NC) in his previous appearance, a 10-rounder Williams lost unanimously May 28 at Barclays Center. Mielnicki, of Roseland, New Jersey, improved to 12-1 and produced his eighth knockout.

With just over a minute to go in the sixth round, Mielnicki landed a right hand that affected Williams. They got tied up several seconds later, but Callas called a halt to the action because Williams’ trainer stepped up on the ring apron and asked for their fight to be stopped.

Mielnicki caught Williams with a hard right hand to his chest in the fifth round. A jarring jab by Mielnicki knocked Williams off balance early in the fourth round.

Williams slowed down Mielnicki during the first half of the third round, but Mielnicki nailed him with two right hands to the side of his head toward the end of the third round.

Mielnicki caught Williams with a right hand in the beginning of the second round, which caused Williams to hold Mielnicki’s left arm for an extended period. Mielnicki continued to land the flusher punches for the remainder of the second round.

Mielnicki connected with several hard right hands during the final minute of the first round. The younger, stronger fighter also worked well off his jab in those opening three minutes.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.