ISTANBUL — Serena Williams cruised into the final of the WTA Championships by beating Agnieszka Radwanska of Poland 6-2, 6-1 Saturday and will play Maria Sharapova for her third title at the event.
Sharapova beat Victoria Azarenka 6-4, 6-2 in the second semifinal, a day after Azarenka had made sure of finishing the year as the top-ranked player.
Sharapova will finish No. 2 even if she beats Williams in today's final.
Williams was never challenged by the fourth-ranked Radwanska apart from dropping serve in the fourth game of the first set.
Radwanska spent more than eight hours on court in her previous three matches, while Williams required less than five to win her three round-robin matches. The difference showed, although Williams did not think that was the case at the start of the match.
"I definitely had an idea that she was tired," Williams said.
To reach the semifinals, Radwanska beat Sara Errani in a match that took 3 hours, 29 minutes — the longest best-of-three-sets match in WTA Championships history.
Sharapova, who rose to No. 1 briefly after winning the French Open, clinched the match against Azarenka when she held to lead 5-1 in the second set after prevailing in a 15-minute game that went to nine deuces, the last one on a double-fault by Sharapova.
Azarenka, of Belarus, ended her best year on a losing note but she became the first woman to reach the $7-million mark in prize money for a year.
At Basel, Switzerland, Roger Federer and Juan Martin del Potro advanced to the final, setting up a rematch of their epic semifinal at the London Olympics.
Top-ranked Federer brushed aside Paul-Henri Mathieu of France 7-5, 6-4 in the semifinals after Del Potro eased to a 6-2, 6-2 win over third-seeded Frenchman Richard Gasquet.
Federer has beaten Del Potro all six times they have met this season, though he was pushed to his limits on Centre Court at Wimbledon in August. Federer won 19-17 in the decisive third set.
Del Potro let a two-set lead slip in their quarterfinal at Roland Garros, and took the first set at the Olympics before losing the second on a tiebreaker.
Federer, chasing his sixth title in seven years at his hometown event, fired 10 aces and never allowed 101st-ranked Mathieu a break-point chance.
Del Potro improved to 16-1 on indoor hard courts in 2012, with his only loss coming against Federer in the Rotterdam final in February.
At Valencia, Spain, top-seeded David Ferrer reached the final for a fourth time, beating Ivan Dodig of Croatia 6-4, 6-7 (5), 6-1 on Saturday.
Ferrer will face Alexandr Dolgopolov in today's final after the Ukrainian used his big serve to ease past Jurgen Melzer of Austria 6-4, 6-2 in the other semifinal.