Jan Hernych advanced to the quarter-finals of the Mercedes Cup on Thursday with a 7-6 (7/5) 0-6 7-6 (7/5) triumph over Argentina's Brian Dabul.

Hernych is ranked 139th in the world, but he caught a break this week when top-seeded Rafael Nadal withdrew from this event at the last minute due to a knee injury.

Nadal, the defending champion and world number two, captured the first Wimbledon title of his career on Sunday.

The Spaniard's decision not to back up his famous victory in Stuttgart has opened the door for Hernych, who became the lucky loser in place of Nadal and received a first-round bye in the process.

The 29-year-old improved to 2-4 this season with Thursday's victory and is in his first ATP quarter-final since February 2007 in Las Vegas.

He will be bidding for his first semi-final appearance since 's-Hertogenbosch in 2006 on Friday when he faces eighth-seeded Argentine Eduardo Schwank, a 7-6 (7/5) 6-2 winner over German wild card Andreas Beck.

Schwank's countryman, Juan Martin Del Potro posted the upset of the day with a 6-3 3-6 6-3 victory against fifth-seeded Italian Simone Bolelli.

The 19-year-old's opponent in the quarter-finals will be fourth-seeded German Philipp Kohlschreiber who defeated Yuri Schukin 6-3 6-3.

The highest remaining seeded here, number two Richard Gasquet of France, will play Spain's Albert Montanes in Friday's quarter-final action.