Angelique Kerber's tennis season has come to a somewhat premature end after she lost 3-6, 3-6 to Sloane Stephens in her third and final match of the WTA Finals in Singapore.

The world number two failed to convert seven break points in the first set and found herself 4-2 down after Stephens broke her serve.

Kerber also fell behind quickly in the second set before battling back to 3-3, but a misfired forehand gave Stephens the match-winning break the American needed to see out the match.

The 30-year-old Wimbledon champion, who was the top seed at the WTA Finals, finished the round robin stage with a record of only one win and two losses. Kerber has now lost five straight matches against Stephens, her only win against the American coming in 2012.

Stephens advances to the final four with a perfect 3-0 record, the first WTA Finals debutant to do so since Spaniard Garbine Muguruza in 2015. She is set to play Karolina Pliskova in Saturday's semifinals while Kiki Bertens, the lowest seed, will play Elina Svitolina after US Open champion Naomi Osaka retired following a 6-3 first set loss.

dv/jh (AFP, dpa)