NEW YORK — Gael Monfils follows his own rules.
The guy does things on a tennis court no one else has — or can. Just search his name on YouTube and watch any of many video clips showcasing his speed and agility; start with the parallel-to-the-ground, a-few-feet-in-the-air dive at this year’s French Open.
He sips soda during breaks in his matches, raising the can in a toast to his agent.
He is currently without any coach at all, in an era when some players have two.
What Monfils has never done, despite all his talent — and in some cases, because he has appeared to value style over substance right there on court, in the middle of a point, preferring the spectacular to the sufficient — is reach a Grand Slam final. He took a step closer Tuesday at the U.S. Open during a surprisingly matter-of-fact 7-5, 7-6 (6), 7-5 victory in the fourth round over No. 7-seeded Grigor Dimitrov, a man considered one of the sport’s up-and-comers.
There is a narrative building around the 20th-seeded Monfils’ success so far this year at Flushing Meadows, where he hasn’t dropped a set en route to reaching the quarterfinals for the first time since 2010: He has matured, is playing more carefully, more seriously.
The Frenchman rejected that notion after Tuesday’s win.
“I’m the same. So I will say I’m a bit more lucky than I was maybe sometime in the past. I think I haven’t changed a lot, to be honest. I haven’t changed a lot,” Monfils said. “I just play maybe solid today, but I’m still the same.”
As if to prove that, there was the unusual sequence in the second set. Trailing 40-love as Dimitrov served, Monfils stood halfway between the baseline and the service line to receive, and then casually and halfheartedly flicked a return long to lose the game. He walked to the changeover to a chorus of boos from the spectators in Arthur Ashe Stadium, plopped down for the break, chucked a towel at the adjacent chair and started barking something toward his guest box in the stands.
Asked about that afterward, Monfils said he was angry at himself at that moment and just wanted to get that game over with.
“I was like, ‘Just serve, because obviously I give you the game. So it’s OK,’” he said. “It’s nothing against anyone. I was upset.”
In the quarterfinals, Monfils will face the winner of Tuesday night’s match between 17-time major champion Roger Federer and 17th-seeded Roberto Bautista Agut.
The other quarterfinal matchup on that half of the draw will be No. 14 Marin Cilic against No. 6 Tomas Berdych or 20-year-old Dominic Thiem. Cilic edged No. 26 Gilles Simon, who was treated for a back problem early on, 5-7, 7-6 (3), 6-4, 3-6, 6-3.
In women’s quarterfinal action Tuesday, 39th-ranked Peng Shuai of China ended the precocious run of 17-year-old Belinda Belic of Switzerland 6-2, 6-1.
Peng, 28, advanced to her first Grand Slam semifinal in the 37th major tournament of her career; only five women took longer to get to the final four at one of the sport’s top four events.