Serena Williams stormed into the final of the WTA hardcourt tournament at Stanford on Saturday, winning the last eight games of a 7-5 6-0 victory over Andrea Petkovic.

The world No.1 and top seed, playing her first tournament since a disappointing Wimbledon campaign shadowed by a viral illness, couldn’t separate herself from the eighth-seeded German in the early going.

They battled to 5-5 in the opening set, with Petkovic saving the only break point in those first 10 games, but after holding for a 6-5 lead, Williams turned the tide in the 12th, finally converting her fifth set point against Petkovic’s serve.

There was no stopping the 17-time grand slam champion from there.

After a first set lasting 50 minutes she polished off the second in 27, breaking Petkovic a fourth time when the German sent a forehand long on match point.

Williams will face the winner of Saturday night’s semi-final between third-seeded German Angelique Kerber and US veteran Varvara Lepchenko.