Austin “Ammo” Williams withstood heavy artillery and survived some adversity against late-replacement opponent Ivan Vazquez to score a ninth-round stoppage win Saturday in Frisco, Texas.

Vazquez (11-1-2, 8 KOs) was a familiar foe for Williams (19-1, 13 KOs), as the pair had shared nearly 60 rounds of sparring together in recent years. Williams came into their middleweight matchup scheduled for 10, stating he was sad for the punishment he was about to administer to an opponent he considered a friend.

But Vazquez proved he wasn’t there for a paycheck, turning in a valiant performance until he ran out of gas in the second half of the fight.

The end of the fight officially came 36 seconds into the ninth round, right after the fading Vazquez was knocked down with a hard right uppercut and straight left hand. Vazquez got up and walked around the ring, but told referee Mark Calo-oy he could no longer continue.

It was the first time Vazquez was fighting past the eighth round of his 11-year career, and the disparity in experience proved to be the final factor.

“This fight was psychological,” said Williams, The Ring’s No. 9-ranked middleweight. “I got matched to fight my friend. It’s supposed to be a ruthless sport, but I had to switch gears in my mindset and adjust to knockout my friend.”

Williams outlanded Vazquez 153-124, according to CompuBox.

Vazquez replaced Williams’ original opponent Etinosa Oliha on Wednesday after he was forced to pull out of their IBF title eliminator due to an eye issue that was flagged during pre-fight medicals. Vazquez had a six-rounder scheduled for Saturday on another card, and he stepped in for the showcase opportunity.

He proved he belonged early on.

Williams, who was clipped by a vicious left hook, hit Vazquez with a violent low blow seconds later in the second round. Vazquez fell to both knees, halting any momentum he could have possibly mounted. But Vazquez recovered quickly and rocked Williams with a big right hand.

In the opening seconds of the third, Williams hit Vazquez with another low blow, and this time he was deducted a point. But he picked up the pace, and his punches, by outmuscling the fellow Houstonian for the rest of the frame.

While the southpaw Williams charged forward, Vazquez stood in range and backed him up with two big winding and well-timed uppercuts in the fourth.

Coach Kevin Cunningham implored Williams to let his hands go after the fourth, and he did just that with several shoeshine attacks in the fifth and sixth rounds. While Vazquez was caught in the corner, he answered back admirably with thudding body shots — he landed 60 in total for the fight.

Williams hit Vazquez with another borderline low blow in the seventh and received another hard warning. Vazquez retaliated with big shots to the ribs, but Williams was unbothered and hit him with a huge left hand and two rights that followed in the closing seconds of the round.

Vazquez continued digging for the body in the eighth and momentarily slowed down his foe. While Williams appeared hurt, Vazquez looked completely fatigued as the pressure mounted until it became too much to handle in the ninth.

“It was a great fight,” said Vazquez, who admitted he got gassed at the end. “I was obviously training for a six-round fight. It’s the people’s opinion if they think I belong on this level.”

The bout took place at The Ford Center at The Star as part of the Matchroom Boxing card on DAZN headlined by the super flyweight title unification fight between The Ring and WBC champion Jesse “Bam” Rodriguez and WBO title holder Phumelela Cafu.