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 US 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.
The Frenchman, who will face Roger Federer for a spot in the semifinals, rejected that notion after Tuesday's win.
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.
"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."
Monfils' lone Grand Slam semifinal appearance came at the 2008 French Open, when he lost to Federer, part of a 2-7 career mark against the 17-time major champion.
Federer advanced to the US Open quarterfinals for the 10th time in 11 years by eliminating 17th-seeded Roberto Bautista Agut 6-4, 6-3, 6-2 Tuesday night. Federer won the point on 35 of 52 trips to the net.
"Coming to the net requires a lot of agility and explosivity and all that stuff -- and I have it back," Federer said. "I'm happy I'm feeling good at net, too, because you've got to anticipate some and read some and it's working really well. So I hope I can keep it up."
A year ago at this time, Federer was dealing with a bad back, but things are different these days.
"Because of the issues I had last year, I had to be unbelievably careful what I did. We had to cut back on a few things I usually would do, but were scared to do. That was not what I wanted to do," he said about his fitness work. "Sometimes if that's what it is and it means don't run on the treadmill or don't do jumps or whatever it is, well, there's other ways you can train that. I'm happy that basically today I can do whatever and I don't have any more setbacks."
The other quarterfinal matchup on that half of the draw will be No. 6 Tomas Berdych against No. 14 Marin Cilic. Berdych beat 20-year-old Dominic Thiem 6-1, 6-2, 6-4; Cilic was a 5-7, 7-6 (3), 6-4, 3-6, 6-3 winner against No. 26 Gilles Simon, who was treated for a back problem early on.
In the afternoon, with the temperature topping 90 degrees (32 Celsius) and the humidity at about 50 percent, Monfils and Dimitrov appeared sluggish at times.
"Where should I begin?" said Dimitrov, a Wimbledon semifinalist in July. "Just a bad match for me."
A key moment came in the second-set tiebreaker, when Dimitrov went ahead 6-4. On the first set point, Dimitrov nearly lost his balance as he shanked a forehand off Monfils' mediocre drop shot.
"One of the worst drop shots I ever hit," Monfils said, grinning, "and he hit a frame."
On the second, a 13-stroke exchange, Dimitrov dropped a backhand into the net.
That was part of four-point run for Monfils thanks to miscues by his opponent. While Monfils essentially kept the ball in play, taking some pace off and pushing shots over the net, Dimitrov sailed forehands long to end the set.
"He defended when he had to," Dimitrov said. "But if you think about it, I did a lot of unforced errors."
What mattered in the end, of course, was who won, something that has not always seemed to matter to Monfils.
"For me, tennis is a sport, you know," he said. "It's not a job, you know. It's a sport."
Information from The Associated Press was used in this report.