Ronda Rousey uses a new twist to beat Sara McMann in UFC 170

Ronda Rousey’s armbar streak is over. Her attention is now on the opponent’s liver.

Rousey successfully defended her Ultimate Fighting Championship women’s bantamweight title Saturday night at Mandalay Bay, delivering a left knee to challenger Sara McMann’s stomach area, a notoriously painful liver shot that ended the bout by technical knockout 1 minute 6 seconds into the first round.

“I knew if I zoned in on that one spot … ,” Venice’s Rousey (9-0) said after a victory that followed eight straight wins by armbar submission.

“We spend a lot of time … focusing on body shots, on knees. I’m learning still. It took a long time for me to learn not just the judo I learned as a kid. ... I feel I’m more well-rounded as a martial artist. I’m not just looking for one finish. I’m looking for what’s available.”

After the fight opened with an exchange of punches, Rousey pressed McMann to the cage and originally landed a right knee toward the belly before switching legs on the attack.

The Rousey left knee dug in, McMann crumpled to the canvas, clutched at her body and couldn’t rise, as referee Herb Dean leaned in and stopped potential Rousey punishment.

The stoppage seemed premature, and the crowd booed Rousey.

“I got hit in the liver,” McMann (7-1) said. “No matter how hard you train, you get hit in the liver. ... I felt like I couldn’t move for a split second, heard [Dean’s] voice and I was trying to get back up, but it’s my own fault.”

Asked if Dean interrupted unnecessarily, McMann said, “It did seem kind of quick. ... You see a fighter down like that, it’s his job to protect us. I should’ve got up quicker.”

Rousey and UFC President Dana White said they thought it was a good stoppage.

“I didn’t think it was too soon,” Rousey said. “I would’ve kept going if someone didn’t stop me.”

Said White: McMann “dropped to her knees, and turned her head the other way.”

Following this conquest of the 2004 Olympic wrestling silver medalist, Rousey heads to filming the “Entourage” movie in mid-March, and said she expects to fight again by the late summer.

In the co-main event, Daniel Cormier not only wanted to quickly make a name for himself upon arrival in the UFC light-heavyweight division, he wanted to close the trap of opponent Patrick Cummins.

Cormier needed just 79 seconds to knock out his former training partner from Dana Point.

San Jose’s Cormier, the former Strikeforce heavyweight champion, moved down in weight to avoid a possible showdown with his close friend and sparring partner Cain Velasquez, the UFC heavyweight champion.

He was originally supposed to meet former light-heavyweight champion Rashad Evans, but when Evans was injured, the UFC found former Penn State wrestler Cummins (4-0), who claimed he made Cormier cry in training.

Cormier was beside himself, vowing to win by destruction.

He did, belting Cummins with early big rights, hammering his jaw with a right uppercut and dropping him with a right followed by 10 punches to Cummins’ head as he kneeled on the mat, bringing the end to the fight by technical knockout.

“When you talk, you’ve got to be able to back it up,” Cormier said.

When asked where he fits in the division with a title fight between champion Jon Jones and Glover Teixeira coming in April, Cormier (14-0) said, “Right at the top.”

Strikeforce heavyweight champion, moved down in weight to avoid a possible showdown with his close friend and sparring partner Cain Velasquez, the UFC heavyweight champion.

lance.pugmire@latimes.com

Twitter: @latimespugmire