Claressa Shields (12-0) remains undefeated, eyes bout with rival Savannah Marshall

Claressa Shields unanimously out-pointed Ema Kozin to set up a potential unification title fight with rival champion Savannah Marshall.

Shields (12-0, 2 KOs), who is No. 3 in ESPN's latest women's pound-for-pound rankings, retained her WBC, WBA and IBF world middleweight titles with a dominant points win over the Slovenian Kozin (21-1-1, 11 KOs).

The 26-year-old American won every round according to the three judges, who scored it 100-90.

Shields made a fourth defense at middleweight in front of Marshall, who was ringside. But Shields perhaps left a little frustrated at not securing a stoppage win in a fight she completely dominated.

Shields fought in Cardiff as the first fight in a multi-bout deal with 28-year-old English promoter Ben Shalom, who plans on matching Shields later this year with Marshall, (11-0, 9 KOs), 30, who holds the fourth world middleweight title.

Marshall, who beat Shields as an amateur, defends her WBO middleweight title against former champion Femke Hermans, who took Shields to points in 2018, in Newcastle on March 12.

After Shields' fight, the rival champions had an angry exchange at ringside.

"The girl I want is Savannah Marshall," Shields said. "I did my job, now she has to do her job on March 12 and then hopefully we can get it on.

"I thought there was plenty of times when the referee should have stopped it, she's definitely going to feel it when she goes home. I give myself an A-.... The only thing I didn't get was the damn knockout. But she took a beating for ten rounds."

It was a happy return to fighting in the United Kingdom for Shields, who won the first of her two Olympic gold medals at London in 2012.

Shields, who has recently trained at former champion Floyd Mayweather's gym in Las Vegas, was impressive on her return to the boxing ring after two MMA fights last year.

Shields, who has won world titles in three weight classes, started opening up more in the second round; her two quick right-hands stunned the 23-year-old Kozin.

The champion's hand speed was too much for Kozin, and Shields attacked the body later in the fourth.

Shields was aggressive and had no difficulty in landing punches, but the courageous Kozin refused to buckle.

Also on the undercard, English lightweight Caroline Dubois made a successful professional debut with a six-round win over Lithuania's Vaida Masiokaite.

Dubois, 21, from south London, the younger sister of heavyweight contender Daniel Dubois and who boxed for Great Britain at last summer's Olympics, almost forced a knockdown in the third round and dominated every round.