It was an eventful undercard on Saturday's UFC Fight Night at the Sprint Center in Kansas City, Missouri. Brett Okamoto runs down all of the action, including a pair of division-altering results, that happened in the lead-up to the main event between record-seeking flyweight champion Demetrious Johnson and challenger Wilson Reis.

Namajunas stops Waterson, eyes strawweight title shot

Rose Namajunas likely locked up her second UFC strawweight title shot on Saturday, and looked like an absolute superstar in the process.

Namajunas (6-3) submitted Michelle Waterson via rear-naked choke at 2:47 of the second round, in the co-headlining bout of UFC Fight Night.

The finish came after Namajunas dropped Waterson with a perfect right head kick to the chin. Waterson (14-5) went flying across the mat from the kick, and Namajunas immediately chased her down and began unloading punches for the finish. Eventually, Waterson gave up her back and succumbed to Namajunas' choke.

The win likely sets up Namajunas to face the winner of a strawweight title fight between undefeated champion Joanna Jedrzejczyk and Jessica Andrade at UFC 211 on May 13.

"I feel I can win the belt and hold it for a long time," said the 24-year-old Namajunas. "Joanna, or whoever wins that fight, I'm coming for you."

Waterson (14-5) hugged Namajunas immediately after the loss. "The Karate Hottie" went into the bout with a lot of momentum, but struggled to hang with Namajunas in every aspect.

After an early Waterson takedown, Namajunas scrambled to take her back and eventually end up in top position. She landed several hard elbows on the ground and scored a takedown of her own later in the round, after Waterson managed to work to her feet.

In December 2014, Namajunas fought Carla Esparza for the UFC's inaugural 115-pound title. Namajunas lost via submission in the third round. She has gone 4-1 since.

Robert Whittaker, right, earned a career-defining victory over Jacare Souza with a second round knockout. Jamie Squire/Getty Images

Whittaker upsets Jacare, shakes up rankings

A major shakeup is coming to the middleweight rankings following Robert Whittaker's upset TKO win over Ronaldo "Jacare" Souza.

Whittaker (18-4) finished Souza (24-5) with strikes on the ground at the 3:28 mark of the second round. The finish came after Whittaker had dropped Souza with a right hand and badly hurt him with two head kicks. It is his ninth career knockout.

Coming into the fight, Souza had won seven of eight in the UFC. He signed an eight-fight contract extension earlier in the week, and UFC president Dana White called him a potential future champ.

It was Whittaker, 26, who looked like a world beater though. He stuffed the majority of Souza's takedown attempts and scrambled quickly back to his feet when the action did hit the floor in the first.

He dropped Souza with a straight right less than 30 seconds into the second round, but refused to follow the submission ace to the floor. After beckoning him up, Whittaker calmly stalked him down with punches and cracked him with two right head kicks that basically finished off the Brazilian. Sensing a finish, Whittaker followed Souza to the ground after he fell back from the second kick.

Fighting out of Sydney, Australia, Whittaker is now on a seven-fight win streak. He called out champion Michael Bisping postfight. The two were supposed to square off in 2015, but Bisping pulled out with an injury.

Renato Moicano, right, earned a split-decision victory over 10-year UFC veteran Jeremy Stephens Saturday night in Kansas City. Jamie Squire/Getty Images

Moicano neutralizes Stephens' power, takes decision

Featherweight Renato Moicano (11-0-1) picked up the biggest win of his career, edging past Jeremy Stephens (25-14) via split decision (29-28. 29-28, 28-29).

Moicano, of Brasilia, Brazil, utilized his reach well. He constantly circled away from Stephens' notorious power, while regularly scoring with leg kicks and jabs.

Stephens appeared to figure Moicano out in the second round, as he cornered him several times along the fence and landed a few heavy shots to the body. He spent most of the first and third rounds chasing Moicano around the Octagon, however, and also gave up two takedowns. ESPN.com scored the fight for Moicano as well, 29-28.

Fighting out of San Diego, Stephens falls to 2-5 in his past seven. Moicano is now 3-0 in the UFC.

After an early onslaught from Roy Nelson, left, in the first round, Alexander Volkov took control and earned his second career UFC victory. Ron Chenoy-USA TODAY Sports

Volkov outpoints Nelson, moves to 2-0 in Octagon

Russian heavyweight Alexander Volkov (28-6) improved to 2-0 in the UFC with a decision win over fan favorite Roy Nelson (22-14). All three judges scored it for Volkov, 30-27.

Nelson, 40, had some success wrestling Volkov early, but appeared gassed by the second round. When he did have Volkov down, he did very little damage. Referee Dan Miragliotta stood Nelson up from top position late in the first round.

Volkov racked up offense with front kicks to the body and a handful of right hands. He had Nelson covering up at the end of the opening round, with a flurry near the fence.

A former Bellator MMA champion, Volkov has now won four in a row.