Updated

Flushing Meadows, NY (SportsNetwork.com) - Gael Monfils reached his second career U.S. Open quarterfinal by upsetting seventh-seeded Grigor Dimitrov on a steamy Tuesday in New York City.

The 20th-seeded Monfils handled the Wimbledon semifinalist Dimitrov 7-5, 7-6 (8-6), 7-5 at Ashe Stadium. The flashy Frenchman Monfils has yet to lose a set at this fortnight.

Dimitrov, who dates women's superstar Maria Sharapova, struggled mightily with his serve and backhand on Day 9 and succumbed to Monfils in 2 hours, 24 minutes. The ultra-athletic Monfils popped 14 aces and was broken only once by his Bulgarian counterpart.

The 6-foot-4 Monfils also reached the quarterfinals at the French Open in June and is now a six-time Grand Slam quarterfinalist.

The former top-10 star Monfils, who turned 28 on Monday, will meet the Roger Federer-Roberto Bautista Agut winner in the round of eight at the USTA Billie Jean King National Tennis Center. The Wimbledon runner-up Federer owns a men's-record 17 Grand Slam singles titles, including five in New York, where he was a runner-up in his last U.S. Open final in 2009. He's 70-9 lifetime in Flushing.