Juan Martin del Potro loses in quarterfinals at Sydney International

Defending champion Juan Martin del Potro was beaten in the quarterfinals of the Sydney International on Thursday, losing 7-6 (5), 7-6 (3) to Kazakhstan qualifier Mikhail Kukushkin.

Del Potro, the 2009 U.S. Open champion returning from an 11-month injury layoff, needed a wild-card entry to get into the main draw because his world ranking had dropped to 338.

"I got lucky playing three matches in this tournament against good players," del Potro said. "I'm here, I'm still alive. I feel tired, but OK."

Kukushkin will next play Argentina's Leonardo Mayer, who beat Julien Benneteau of France 6-3, 7-6 (4).

Wimbledon champion and second-seeded Petra Kvitova beat Tsvetana Pironkova of Bulgaria 7-5, 6-1 to advance to the women's singles final. Kvitova will play Karolina Pliskova, who beat Germany's Angelique Kerber 6-3, 6-2.

At the Heineken Open in Auckland, New Zealand, fourth-seeded Kevin Anderson of South Africa became the only seeded player to reach the semifinals when he beat American Steve Johnson 6-4, 7-6 (8) in a match that pivoted on a line call in the second-set tiebreak.

Johnson hit a backhand passing shot at 7-7 that seemed to clip the line, giving him the chance to serve for the set. But the shot was called out, the point went to Anderson and he was able to clinch the set and match, having previously spurned the opportunity when serving for it at 5-4.

"That was a real high-quality match," Anderson said. "I played really well from the beginning."

Anderson will play Jiri Vesely after the Czech qualifier beat American Donald Young 6-2, 6-3 to reach an ATP Tour semifinal for the first time.

Lucky loser Lucas Pouille of France beat Albert Ramos-Vinolas of Spain 6-3, 6-2 and Adrian Mannarino of France beat another lucky loser, Alejandro Falla of Colombia, 6-3, 6-1 to set up the other semifinal.

At the rain-affected Hobart International, Britain's Heather Watson advanced to the semifinals with a 7-6 (0), 6-2 win over ninth-seeded Roberta Vinci of Italy.

American Alison Riske also won her quarterfinal, beating Zarina Diyas of Kazakhstan 6-3, 6-0.

In a second-round match, Karin Knapp of Italy defeated top-seeded Casey Dellacqua of Australia, 7-5, 2-6, 6-3.