NEW YORK – Frank Sanchez seemed destined for what would’ve been his third straight 10-round points win Saturday night.

Then “The Cuban Flash” caught Carlos Negron with a right hand that changed the course of their heavyweight fight in the ninth round at Barclays Center in Brooklyn. Sanchez dropped Negron with that shot and finished him off later in the ninth round after landing several flush punches that made referee Ricky Gonzalez step between them while Negron was still standing.

The official time of the stoppage was 1:36 of the ninth round on the Deontay Wilder-Robert Helenius undercard.

The 30-year-old Sanchez (21-0, 14 KOs) became the fourth heavyweight to stop Puerto Rico’s Negron (25-4, 20 KOs) inside the distance. Dominic Breazeale (ninth round) and Brian Howard (first round) knocked him out in back-to-back bouts in 2018 and 2019 and Epifanio Mendoza stopped him in the third round in September 2011.

Sanchez’s previous two fights, unanimous victories over Nigerian contender Efe Ajagba and German veteran Christian Hammer, both went the 10-round distance.

Sanchez finally floored Negron with a right hand that knocked him awkwardly to his knees with 2:26 on the clock in the ninth round. Negron beat Gonzalez’s count and tried to fight out of the trouble, but Sanchez blasted him with a combination that made Gonzalez step between them while Negron was backed against the ropes.

A lunging left hook by Sanchez backed Negron into the ropes with just over 1:15 on the clock in the eighth round.

Negron, after waving off the effects of a right hand Sanchez landed, shoved Sanchez to the canvas with just over 1:10 on the clock in the seventh round.

Sanchez drilled Negron with a right hand that wobbled him with just over a minute to go in the sixth round. Sanchez sensed Negron was hurt and tried to follow up, but Negron regained his senses and made it to the end of the round.

Sanchez cracked Negron with a right hand about a minute into the fourth round, but Negron shook his head to indicate it didn’t affect him. Gonzalez warned Sanchez and Negron for a clash of heads with just under 45 seconds to go in the third round.

Negron landed a right hand to the side of Sanchez’s head 1:05 into the second round.

Sanchez was very aggressive in the first round and landed several right hands in the first two minutes of it. He continued to pressure Negron until the opening round ended.

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