Serena Williams overcame a tough first set, gathering steam to roll through the second set with a 7-5, 6-0 victory over Andrea Petkovic in the Bank of the West Classic semifinals on Saturday.

The top seed and world No. 1 dominated Petkovic, the No. 8 seed, winning the final eight games of the match. Petkovic earlier knocked off Serena's sister Venus in their Friday quarterfinals match.

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Petkovic put up to Williams early on, making the match a close one in the first set. But Williams gained momentum after taking control, 6-5, with Petkovic falling behind 0-40. Petkovic rallied to gain advantage at one instance, only to lose three straight points to Williams who claimed the set.

Clearly rejuvenated after taking a breather from professional game, Williams took control of the second set, but Petkovic made one final stand in the third game. She managed to engage Williams in a wild 19-stroke rally which Petkovic won. She tried working to break point but Williams snuffed the fight out of her, winning the next three straight points to hold serve.

Petkovic had a crack at making an unusual achievement of beating both the Williams sisters consecutively at a tournament. She was the ninth player to attempt doing that, and the first since 2010.

Petkovic quelled Venus Williams' run on Friday, sending the former top-ranked player home with a 6-1, 3-6, 7-5 victory.

Venus bounced back at the second set after yielding the first, but Petkovic rallied in the third set to defeat Venus in their first meeting since 2012.

Serena Williams will face the winner of the other semifinal match between No. 3 seed Angelique Kerber and the unseeded Varvara Lepchenko.