ISTANBUL — Serena Williams, in obvious discomfort and walking slowly during changeovers, struggled past Jelena Jankovic 6-4, 2-6, 6-4 on Saturday and will play Li Na in the final of the WTA Championships.
Li advanced to her first WTA Championships final by sweeping 2011 winner Petra Kvitova 6-4, 6-2, setting up a showdown today between the two oldest players in the tournament.
It's only the second time in the history of the event that two players over 30 — Williams at 32 and Li at 31 — have made it to the last four. The season-ending tournament brings together the top eight players in the world.
It was not clear what was bothering Williams. She did not move well on the court and frequently held her head wrapped in a towel during changeovers. Williams tried to keep the points short and often winced.
Jankovic was unable to take advantage of whatever was bothering Williams, who is one win from her fourth WTA Championship and 11th title of the year.
Williams wasted a match point and failed to serve out the match at 5-2, and Jankovic won two straight games. Williams squandered two more match points before finally closing it out with a smash.
At Valencia, Spain, defending champion David Ferrer beat former winner Nicolas Almagro 6-2, 6-3 to advance to the Valencia Open final.
Ferrer will play Mikhail Youzhny, a 6-2, 6-4 winner over Dmitry Tursunov in an all-Russian semifinal.
At Basel, Switzerland, Roger Federer set up a rematch with Juan Martin del Potro for his hometown Swiss Indoors title by beating Vasek Pospisil in the semifinals.
Federer advanced to his eighth straight Basel final with a 6-3, 6-7 (3), 7-5 victory over the 40th-ranked Canadian.
Earlier, defending champion del Potro beat Edouard Roger-Vasselin of France 6-4, 4-6, 6-2.