Claressa Shields continues to prove her dominance, even well outside of her comfort zone.

Already one of the greatest female boxers of all time, Shields enjoyed an impressive mixed martial arts (MMA) debut, scoring a 3rd round stoppage of Brittney Elkin. The three-division and reigning lineal junior middleweight and middleweight champion pounded away on a defenseless Elkin until forcing the stoppage of 1:44 of round three in their ESPN2-televised main event Thursday evening at Ocean Casino Resort in Atlantic City, New Jersey.

“I never doubted myself in a boxing match in my life. MMA is something like, it’s possible I can lose this first fight,” Shields admitted during her ESPN2 post-fight interview. “I don’t want to lose but all I could do was just try not to lose. I just had a never quit attitude every round.”

Shields spent more than a year mentally preparing for her debut in MMA, including a solid seven months’ worth of training in different forms of combat sports. Her supreme boxing skills were ultimately her most effective weapon throughout the grueling three round affair, while Elkin controlled the action on the ground especially in the opening round.

The bout started off well-intended for Shields, a two-time Olympic Gold medalist and three-division world champion in the pro ranks as a boxer. Elkin was able to fend off the incoming, taking down Shields and keeping her pinned to the canvas for most of the five-minute round. Shields remained composed, not allowing Elkin to cause any more damage.

The tide turned in round two, as Shields literally came out swinging. A combination from the unbeaten boxing pound-for-pound queen appeared to daze Elkin, though ultimately letting the Bethlehem, Pennsylvania jiu-jitsu specialist (holding a brown belt in that field) off the hook. Elkin once again managed a takedown of Shields, though not enjoying the same level of dominance as in the preceding round. Shields showed her ground and pound skills in order to fight her way out of trouble and ended the round on a high note even if not necessarily winning on the scorecards.

“Every time I sat down in the corner, I was like ‘Damn, I lost another round,’” noted Shields. “I came out for the second round, lost the second round. Then came the third round, my coach said to not get taken down. She got me on the ground but she never hurt me. None of her punches hurt me. None of her armbars—nothing.

“When that third round came, I was there to destroy her.”

From that point, there was no stopping Shields.

Elkin was in trouble for the first time in the fight early in round three. Shields set up the attack with clean punching, sending Elkin to the mat and then pounding away on her head. Elkin remained on the ground as Shields used her lower body strength to position her opponent for the fight ending sequence. Shield continued to strike, repeatedly catching her opponent clean with multiple right hands.

“I just seen that she didn’t like getting hit. She was exposed. Coach kept saying, ‘Let her out.’ I was like, ‘I’m not letting her up.’ She turned toward me. I pushed myself toward her again, and it was over.“

Shields’ fight-ending dominance was well-reflected in final fight stats. The unbeaten 26-year-old landed 90-of-96 total strikes, including 39-of-41 in arm strikes and an even more impressive 49-of-52 on the ground. A large chunk of it came in the truncated round three in forcing a mercy stoppage.

“I went crazy,” Shields noted. “I was not losing. I may have lost those two rounds but I was not losing this fight. I sat there in the corner, they said ‘Go out there and get your KO.’ When he said that, I came out (and did it).”

Shields is now 12-0 overall as a pro in combat sports, 11-0 in her chosen field of boxing and 1-0 (1KO) inside the cage. Elkin’s MMA record falls to 3-7.  

“Brittney is so freaking experienced at everything but she never hurt me,” stated Shields, who was coming off of a 10-round shutout of unbeaten Marie-Eve Dicaire in their undisputed junior middleweight championship boxing match in March. “I just seen that she didn’t like getting hit. She was exposed. Coach kept saying, ‘Let her out.’ I was like, ‘I’m not letting her up.’ She turned toward me.

“I pushed myself toward her again, and it was over.”

The bout served as part of the Professional Fighters League (PFL), with whom Shields signed a multi-fight contract late last fall. Shields will continue to co-exist between the two combat sports worlds, with her goal of becoming the first-ever fighter to simultaneously hold championships in both sports.

Jake Donovan is a senior writer for Twitter: @JakeNDaBox