Serena Williams beats Andrea Petkovic to reach Stanford final

Eighth seed Andrea Petkovic beat Serena Williams' sister Venus 6-2 3-6 7-5 in the previous round

Serena Williams remains on track to win her third Stanford title after sweeping past Germany's Andrea Petkovic to reach the Bank of the West Classic final.

The world number one, playing her first event since recovering from a virus, won 7-5 6-0 and will face another German, Angelique Kerber, in the final.

Williams was back on court 16 hours after a testing win over Ana Ivanovic.

"My body feels great," said the American, 32. "I'm just really excited to be in the finals of Stanford again."

Petkovic, seeded eighth, had beaten Venus Williams in the previous round but found the younger sibling too strong.

Williams added: "Andrea and I both had really long matches yesterday, so I was just hoping to come out again today with fresh legs, and just try to do the best I could out there."

Third seed Kerber came back from the brink of defeat to see off American Varvara Lepchenko.

The German trailed 6-4 5-2 and had to save a match point before winning 4-6 7-6 (7-4) 6-2 in two hours and 39 minutes.

At the Citi Open in Washington, Japan's Kurumi Nara will meet Russian Svetlana Kuznetsova in the women's final, while the men's side will see Milos Raonic take on Vasek Pospisil in the first all-Canadian final on the ATP Tour.

Canada's Pospisil is through to his first ATP final at the age of 24

"Personally, this is a first final for me so that's great," said Pospisil, the world number 36, who beat Richard Gasquet 6-7 (5-7) 6-3 7-5.

"It's more special that I am playing a Davis Cup team-mate and a fellow Canadian."