By Keith Idec

NEW YORK – Shawn Porter wore out Andre Berto on Saturday night.

The relentless Porter’s pressure led to two knockdowns, one apiece in the second and ninth rounds, and a ninth-round technical knockout win in the main event of Showtime’s doubleheader from Barclays Center. Referee Mark Nelson stopped their scheduled 12-round welterweight fight at 1:31 of the ninth round because a bleeding, battered Berto was hurt near his corner, just several seconds after he got up from the second knockdown.

Berto (31-5, 24 KOs), of Winter Haven, Florida, didn’t complain about Nelson’s stoppage.

Porter improved to 27-2-1, produced his 17th knockout and became the mandatory challenger for WBC welterweight champion Keith Thurman (28-0, 22 KOs, 1 NC). Porter lost a 12-round unanimous decision to Thurman on June 25 at Barclays Center, but their fight was very competitive and entertaining.

Thurman told Porter in the ring after he beat Berto that they could fight next.

The Porter-Berto bout, meanwhile, was largely an ugly fight filled with holding, wrestling and accidental clashes of heads. Porter actually apologized to Berto after the fight for the numerous head-butts that led to cuts over the eyes of both boxers.

“I got to clean up those head-butts,” Porter said. “We tried to use the whole ring, but sometimes in the heat of battle, I’m a fighter and Mr. Berto is a fighter as well. Those head-butts were just the two of us going in and fighting.

“My intention is never to use my head as a weapon. This was just a very hard-fought battle by both of us, and I’m blessed to get the victory.”

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Porter scored a knockdown, his second of the fight, early in the ninth round. The ropes held up Berto after Porter landed a left hook, which Nelson correctly counted as a knockdown.

Berto complained that Porter had head-butted him moments earlier, which led Berto to fall into the ropes. Porter pounced on Berto after Nelson allowed the action to resume, hurt Berto again with a left hook and Nelson stopped the fight, with Berto’s back to his own corner.

“I have to give him credit, but he’s a rough fighter,” Berto said. “He has great skills, but at the same time, he’s gonna be rough and try to handle me anyway he can. I got a lot of head-butts, and he did, too. Shawn is a tough competitor. We had a good, competitive fight until the head-butts got to be a little too much for me. But I thought it was a really good fight before that.”

Porter hurt Berto with a straight right hand early in the eighth round. That punch moved Berto into the ropes and enabled Porter to pounce on him.

Porter landed power shots to the head and body, but Berto was able to recover.

Berto had some success in the seventh round, when he was able to fight from a favorable distance and landed several effective punches. Berto went to the canvas in the sixth round, but Nelson ruled it was a slip after Berto threw a punch.

Porter and Berto suffered cuts during a rough fourth round in which Nelson warned both fighters for head-butts.

The cut that opened over Porter’s right eye was the second he sustained in the fight. He already had a nasty gash around his left eye from an accidental clash of heads in the second round. Berto was cut around his left eye in the fourth round.

Fighting with a sense of urgency because of a terrible cut over his left eye, Porter pressured Berto throughout the third round. He landed multiple right hands near the center of the ring, but seemed to smother himself as he tried to do damage against vulnerable Berto.

Porter dropped Berto with a short right hand in the second round, which connected as Berto was attempting to throw a right hand of his own. Berto went down to one knee, but got up quickly.

The round ended soon after Berto got up, so he was able to recover between rounds.

Porter mauled Berto earlier in the second round, when he backed Berto into the ropes and landed several sharp punches. Porter paid a steep price for those exciting exchanges, though, as an accidental clash of heads opened a nasty gash over Porter’s left eye.

Berto landed two solid right hands within the final minute of the first round, but Porter took those shots well.

Both boxers ended long layoffs Saturday night.

Berto hadn’t fought in almost a year, not since he knocked out Victor Ortiz in the fourth round of their rematch last April 30 in Carson, California. Porter’s previous appearance was his unanimous-decision defeat to Thurman nearly 10 months ago at Barclays Center, where they produced one of the most entertaining fights of 2016.

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