NEW YORK – The glamour matchup as the men's fourth round concludes Tuesday is, as usual, anything involving Roger Federer. Federer and his opponent, No. 17 seed Roberto Bautista-Agut, play the 7 p.m. night match on Arthur Ashe Stadium.
But the most intriguing one comes up first: shotmaking Frenchman Gaël Monfils of France vs. Bulgaria's Grigor Dimitrov, who is practically an honorary Frenchman having spent many of his formative years at Serena Williams coach Patrick Mouratoglou's academy there.
Here's how the matches shape up.
 Grigor Dimitrov (BUL) vs.  Gael Monfils (FRA)
Head-to-head: They're 1-1, and the data is inconclusive in terms of choosing a favorite. Monfils defeated Dimitrov in straight straight sets int he first round of the 2011 U.S. Open, when Dimitrov was just 20. Dimitrov won in Bucharest on red clay this summer, up 5-1 when Monfils retired from the match.
Dimitrov, with the exception of that 0-6 set that kicked off his rain-delayed match against David Goffin in the previous round, has been solid. Monfils has been exceptional – playing the way everyone is begging the talented Frenchman to play, nearer the baseline and a little more within himself.
The ending of that U.S. Open match was very nearly a little ... awkward. But very French.
 Roger Federer (SUI) vs  Roberto Bautista Agut (ESP)
Bautista-Agut first came on the radar when he defeated Juan Martin del Potro at the Australian Open earlier this season. It was one of those brutally hot days that can happen in Melbourne; in fact, they actually stopped play on all the courts because of the heat rule. And then there was a rain delay. So late into the night, Bautista-Agut outlasted a player who, as it turns out, has missed most of the rest of the season with a left wrist injury.
In the Spanish scheme of things, Bautista-Agut is easy to overlook with the presence of stellar compatriots like Rafael Nadal and David Ferrer. But he's very solid and, at the age of 26, has snuck into the top 10 nearly unnoticed.
Along the way to his meeting with Federer, he has not had to face a seeded opponent. He was down two sets to one to Andreas Haider-Maurer in the first round before prevailing then beat American Tim Smyczek and French lefty Adrian Mannarino. Federer is a big step up from that.
It's the first meeting between the two.
 Marin Cilic (CRO) vs  Gilles Simon (FRA)
On a very hot day – the hottest in New York this summer – this one could take awhile. And in these types of matchups (as with Milos Raonic and Kei Nishikori late last night), you have to favour the smaller, more compact man to survive the ordeal in better nick.
Simon just never seems to get tired. And he's used to marathons.
Cilic is more of a power player who has a vested interested in not getting into long, extended rallies that expose his movement, which is fine for a big man but inferior to the speedy Simon's.
Simon is 4-0 against Cilic, but it's no surprise that two of those have gone five sets. Only one of those matchups has come since 2008, though; a win by Simon in the second round of the Australian Open after he was down two sets to one.
 Tomas Berdych (CZE) vs Dominic Thiem (AUT)
The battle between the veteran player with the two-handed backhand and the youngster with the classic one-handed is promising, not the least of which because Thiem may have a shot at a U.S. Open quarter-final, at age 20. Well, 21, since it's his birthday on Wednesday.
Berdych has been rather quiet this season, even though his ranking has remained relatively stable. Thiem has defeated close friend and training partner Ernests Gulbis in five sets, then took care of veteran lefty Feliciano Lopez in straight sets.
The two have never met before; coming into the U.S. Open Thiem had 47 matches at the ATP Tour level, 34 of them this season (he was 23-24); Berdych had ... 720.