Canada's Bianca Andreescu was eliminated from the WTA Finals on Wednesday after retiring from her match against Karolina Pliskova with a left knee injury.
Andreescu was leading 2-0 in the first set, with Pliskova serving at 30-15 in the third game, when she came up limping after returning a serve and took a medical timeout.
She had her knee taped and she played through the first set, even challenging Pliskova's serve with three break-point opportunities in the fifth game, but clearly struggled with her movement and retired after losing the set 6-3. Pliskova won on an ace that Andreescu didn't move to return.
Andreescu called for coach Sylvain Bruneau after going down 3-2 and told him she was having trouble bending her knee. He told her not to push it. A visibly upset Andreescu said: ``I don't want to stop.''
The 19-year-old from Mississauga, Ont., is now 0-2 at the season-ending, US$14-million event and can't advance to the semifinals.
Pliskova will advance and play Simona Halep for a semifinal spot. Halep defeated Andreescu in their opening match on Monday.
Earlier, defending champion Elina Svitolina qualified for the semifinals by beating Halep 7-5, 6-3.
Svitolina, the only competitor in the eight-player field not to win a title this season, last won a tournament at last year's WTA Finals.
The Ukrainian is 2-0 in the Purple Group, winning both of her matches in straight sets. Halep is 1-1.
Svitolina broke Halep in the final game of the first set to take the lead. She then broke the Romanian's serve in the eighth game of the second set and held to win.
The victory was Svitolina's fifth in nine matches against Halep. On the four previous occasions in which she won, Svitolina went on to win the tournament.