STANDFORD, California: Top seed Serena Williams came from a set down to book her place in the Stanford Classic semifinals with a hard-earned 2-6, 6-3, 7-5 win against fifth-seeded Serb Ana Ivanovic on Friday.

Serena, whose sister Venus was beaten in three sets by Germany’s Andrea Petkovic earlier in the day, initially struggled on a fast playing surface but gradually found her range to seal victory in just under two hours.

“It wasn’t very easy,” Serena, who will face Petkovic in the last four on Saturday, told ESPN. “Ana plays very well. This surface was a little fast so she was hitting a lot of shots.

“But I just fought it and stayed in there. I just tried to do everything that I worked on.”

Serena was broken in the first game of the match, then double-faulted to lose serve again in the fifth and trail 1-4 before losing the opening set in just under 30 minutes.

However, the American used her crunching ground strokes to great effect in the next two sets and, helped by 10 aces, she wrapped up the win when her opponent sent a forehand service return wide.

Asked how she had adjusted to the slick conditions on the hardcourt surface, Serena replied: “You just start running. You have to see faster, you have to move faster, you have to turn faster, everything you have to do just a little step faster.

“But I am feeling really good. I had some long rallies and I wasn’t out of breath at all so I was like. ‘Yeah’,” added Serena, who suffered a surprise third round loss at Wimbledon in her previous tournament.

Earlier, the eighth-seeded Petkovic battled past Venus Williams 6-1, 3-6, 7-5 in a pulsating match lasting nearly two hours.

Former world No. 1 Venus, who had upset fourth seed Victoria Azarenka in straight sets in the previous round, fought back from 6-1 and 2-0 down to level the match but the German regained control in the decisive third set.

In the other two quarterfinals, third-seeded German Angelique Kerber swept aside Spaniard Garbine Muguruza Blanco 6-2, 6-1 while Varvara Lepchenko crushed fellow American Sachia Vickery 6-1, 6-0.

Goffin wins Kitzbuhel title, extends win streak to 20

In Kitzbuhel, Austria, David Goffin claimed his maiden tour title on Saturday with a 4-6, 6-1, 6-3 win over Austria’s Dominic Thiem in the Kitzbuhel final, extending his winning streak to 20 matches in the process.

The Belgian wild card rallied from an early deficit in the last claycourt match on the ATP World Tour in 2014 with a victory which will also take him into the top 50 next week after being outside the top 100 just a month ago.

“It’s a great day for me, to win an ATP (World Tour) 250,” said 23-year-old Goffin, whose winning streak had been based on two titles on the second-tier Challenger circuit.

“You work so much in the fitness room and on the court for a moment like today. You play so many practices and so many matches to have this emotion, so when you win the match point you can’t control it.”

Goffin is the first Belgian winner on the ATP World Tour since Xavier Malisse claimed victory in Delray Beach seven years ago.

Raonic uses big serve to beat Johnson

Meanwhile, second seed Milos Raonic relied on his powerful serve to blast his way through his quarterfinal match against American Steve Johnson at the Citi Open in Washington on Friday.

Wimbledon semifinalist Raonic took a while to get going but was unstoppable once he found top gear, pounding down 16 aces to beat the unseeded Johnson 7-6(2) 6-2.

The Canadian will meet another unseeded American, Donald Young, in a Saturday semifinal after Young upset seventh-seeded South African Kevin Anderson 3-6 7-6(3) 6-2.

The other semifinal on the hardcourt at the William H.G. Fitzgerald Tennis Center will pit sixth seed Richard Gasquet of France against either Colombia’s Santiago Giraldo or Canadian Vasek Pospisil.

Giraldo and Pospisil had completed just two points in their decisive third set on Friday before the match was suspended because of rain. They are scheduled to resume on Saturday before the winner takes on Gasquet later in the day.

Gasquet had the easiest quarter-final match on Friday, waltzing past Japan’s Kei Nishikori 6-1 6-4 in less than an hour.

Nishikori, the fourth seed, appeared hampered by an ankle injury that restricted his mobility as the Frenchman rode a strong backhand to improve his career head-to-head record to 5-0.

“I saw he had a little problem,” Gasquet told ESPN.