Wawrinka on song in Saint Petersburg

The 33-year-old Swiss star Wawrinka, a wildcard entry who defeated Karen Khachanov, will take on the winner between defending champion Damir Dzumhur and Guido Pella.

Swiss tennis player Stan Wawrinka.   -  Getty Images

Three-time Grand Slam champion Stan Wawrinka advanced to the quarter-finals of the St Petersburg Open on Wednesday with a win over Russian fourth seed Karen Khachanov in two tie-break sets.

The 33-year-old Swiss star Wawrinka, a wildcard entry, knocked off world number 24 Khachanov 7-6 (12/10), 7-6 (7/1) and awaits the winner between defending champion Damir Dzumhur and Guido Pella.

“I'm really happy as the level of my play was really good today,” Wawrinka said.

“We both played really well, really aggressive. I was expecting a tough match and it was really tough. My level was great and I'm really happy with everything that took place on the court today.”

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Wawrinka, the former world number three, who is now down at 88 after a battle with injury, started confidently breaking his rival's serve early.

However the Swiss, who has been struggling to find his best form since returning to the ATP Tour after two operations on his left knee a year ago, suddenly lost his nerve to allow the local favourite to break twice in succession.

Khachanov, 22, was serving for the set but Wawrinka broke again to level and force a tie-break, closing it out at the sixth attempt having also saved two set points. Wawrinka then raced through another tie-break to seal victory over Khachanov in the first meeting between the pair.

Fifth-seeded Spaniard Roberto Bautista Agut and Canada's Denis Shapovalov, the seventh seed, reached round two with respective wins over qualifiers Luca Vanni, 7-5, 6-2, and Adrian Menendez-Maceiras, 7-6 (7/3), 6-2.

Martin Klizan of Slovakia upset Italy's second seed Fabio Fognini, the man he beat in the 2012 final, 6-3, 6-4.

“It was a good match amd I'm very happy with my performance today,” Klizan said.

In the quarter-finals, the left-hander will face the winner of the clash between Shapovalov and Italian Matteo Berrettini.

Meanwhile, 36-year-old veteran Mikhail Youzhny, who is playing the final event of his career, won 7-6 (8/6), 6-4 his opening round match against Mirza Basic of Bosnia. Youzhny, the 2004 champion, is now just one win shy of his 500th career victory.

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