Claressa Shields was on the floor.

She was on national television. Family and friends in Atlantic City at Ocean Casino Resort cheered her on.

At this point, she couldn’t rely on the boxing that made her one of the most accomplished women boxers of all time. She had to grapple her way out of the uncomfortable position that Brittney Elkin had her in.

Shields spent more than half the fight on the floor. By the the start of the third round, it was looking like her sweet MMA debut was headed for a sour ending.

Then boom!

Shields gained control on the floor early in the third round and started pounding her right hand into Elkin’s head repeatedly while Elkin was curled up trying to protect herself. The fight was stopped at one minute, 44 seconds as Shields won her Professional Fighters League (PFL) debut via a third round TKO.

As uncomfortable as some of the fight was, it was the dependable right hand that finished the job.

“I had told myself this is not going to be easy,” Shields said. “That’s why I spent so many months in Albuquerque [N.M.]. I’ve been doing MMA for 7 months, she’s been doing it for 12 years, so I knew I was at a disadvantage but I also knew, too like, I’m just a different kind of animal.”

That right hand flashed early in the first round when Shields threw her first punches. The crowd went “ooh” as Shields’ strike speed reached as high as 19 miles per hour, according to PFL’s Cagenomics. That was the third-highest strike speed of all fighters at PFL 4 on Thursday night.

Elkin, a brown belt in jiu-jitsu, kept her distance and worked to her grappling strengths. She got Shields on the floor early in the first and second rounds, and the two never stood in the center of the cage again in either round. Shields’ goal was to stay in the center as much as possible.

» READ MORE: Claressa Shields has one of the most impressive resumés in boxing. She’s adding MMA on June 10 in Atlantic City.

Even though Shields admitted that this was the first time she entered a fight thinking she could possibly lose, it didn’t show. While Elkin (3-7) controlled a lot of the first two rounds, Shields kept her composure.

“I didn’t freak out because I had been in that position so many times in practice,” Shields said. “I knew she was more tired than me. She didn’t really do any damage to my face or anything.”

The best example of Shields’ composure may have happened in the second round. While both fighters were on the floor, Elkin put her hands on Shields’ arm and attempted to cross her legs around it.

“She’s done,” a viewer at Ocean Resort Casino’s Ovation Hall said about Shields’ chances.

Shields used her strength to snatch her arm away from the arm bar.

“We worked so much on that,” Shields said. “So many trainings. When I saw her going for it, I was like hell no.”

Breaking the arm lock was the final momentum swing. Shields finished the last 15 seconds of the second round strong and controlled the third before the stoppage.

As confident a fighter as Shields is, she knows there’s a lot to clean up in order to achieve her goal of being an MMA champion. PFL star Kayla Harrison, for example, dominated her match with Elkin and won via first-round submission.

All the great MMA fighters have a dependable elite skill. And when her back was against the wall, Shields called on hers.

“My right hand has never failed me,” Shields said.