EASTBOURNE, England - Caroline Wozniacki retired with a back injury three games into her semifinal at the grass-court Nottingham Open on Friday, handing 18-year-old Swiss Belinda Bencic a place in the final against former Wimbledon runner-up Agnieszka Radwanska.

The second-seeded Wozniacki was 3-0 down when she called for her trainer and stretched her leg muscles before deciding she could not continue.

"I have had slight back problems the whole week," Wozniacki said. "Today it stiffened up more and I felt like I couldn't move the way I wanted to and felt pain."

The fifth-ranked Wozniacki said she expects to be fit for Wimbledon, with her first-round match against Saisai Zheng on Tuesday.

Bencic is bidding for her first title, after losing finals in Tianjin in 2014 and 's-Hertogenbosch this year.

Radwanska beat Sloane Stephens of the United States 6-1, 6-7 (3), 6-2 on Friday to stay in contention for a second title at the Wimbledon warm-up tournament.

The ninth-seeded Radwanska clinched the victory on her second match point with a mishit return that crept over the net and beyond the reach of Stephens.

Radwanska served for the match at 6-5 in the second set but Stephens broke before dominating the tiebreaker.

The Polish player, who won the Eastbourne title in 2008, lost to Serena Williams in the Wimbledon final in 2012.

"I will be extra motivated because I (have) never won the same tournament twice so I will try extra hard to win," Radwanska said.

Radwanska and Bencic have never played each other.