Top-seeded Stan Wawrinka and second-seeded Kei Nishikori advanced to the semi-finals of the Geneva Open with come-from-behind three-set victories over Sam Querrey and Kevin Anderson, respectively.

The 32-year-old Wawrinka, who has struggled on clay thus far this season, on Thursday worked out some of the kinks in his game in a confidence-boosting 4-6, 7-5, 6-2 win over Querrey, reports Efe.

The big-serving American took the opening set without losing his serve and then went up an early break of serve in the second set against the defending champion.

But the sweet-hitting Swiss delighted the home crowd by breaking Querrey's serve twice to take the second set and two more times in a comfortable third-set victory.

The third-ranked Wawrinka has a record of just 4-3 on clay this year but is looking to round into form in time for tennis' lone Grand Slam event on that surface, the French Open, which gets underway on Sunday.

In the other matches, Nishikori saved three match points before edging Anderson 2-6, 6-4, 7-6 (8-6).

"There haven't been too many times that I'm down match point and win, so it's great for me. He had more chances, but I served a little bit better in the end. It's important to win some matches like this," the Japanese world No. 9 was quoted as saying on the ATP World Tour's Web site. 

Wawrinka will take on 85th-ranked Russian Andrey Kuznetsov, a 6-2, 1-6, 7-5 winner Thursday night over Germany's Cedrik-Marcel Stebe, in Friday's second semi-final.

The first semi-final will pit Nishikori against German qualifier and serve-and-volley practitioner Mischa Zverev, the world No. 33.