Tien-Khachanov: the quarterfinal comes down to the Russian's first-serve percentage
Learner Tien and Karen Khachanov meet for the first time in their careers tonight on Louis Armstrong, with a quarterfinal spot at the US Open on the line. Tien, world No. 15 and the No. 14 seed, is favored by the bookmakers, and the market has it right, but the match hinges on one thing: how many first serves the Russian lands. Khachanov hit 12 aces to eliminate Felix Auger-Aliassime, the No. 3 seed. As long as his serve holds at that level, Tien's game has no material to work with.
Khachanov's serve takes the rally off the table
Against Benjamin Bonzi (6-3, 6-2, 6-4), Khachanov almost never had to construct a point. That's top ten form, not the form of a No. 50 in the rankings. When the serve is working like that, the rally never opens up: the point ends within three shots, and a counterpuncher sees few balls to play.
The template for this match is the second round. Auger-Aliassime won the first set in a tie-break and then dropped three straight, 6-7(5), 6-3, 6-2, 6-2, finishing with 47 unforced errors against the Russian's 30. When Khachanov holds his service games without facing break points, the opponent starts pressing on return just to stay in the point. The Canadian, who was off that day, fell into that trap after a set and a half.
The threshold to watch in the first two sets is simple: above 65% first-serve percentage, Khachanov dictates the rhythm of his own service games. Below 60%, the match turns into the one Tien wants to play.
Tien's second serve is the target, and Khachanov knows how to hit it
Tien doesn't serve hard. His average first-serve speed has grown over the past year, real progress, but the serve remains the weakest part of his game. The lefty compensates with geometry: the wide serve from the ad court pulls a right-hander off his backhand and opens the court for the next shot.
The problem is that Khachanov doesn't give the second serve away for free. He's an aggressive baseliner, he steps in to take time away instead of sitting back and waiting for the error, and he's the kind of opponent who punishes a short second serve. The edge Tien usually builds in return games shrinks here. Tien will need to keep his first-serve percentage high, because his usual safety net, the extended return game, pays off less tonight.
Khachanov eliminated Auger-Aliassime, the No. 3 seed, with 12 aces and 30 unforced errors against 47.
Two opposite roads to the fourth round
Khachanov has spent very little energy: 6-3, 6-0, 6-1 over Roman Burruchaga, three sets against Bonzi, and in between one long match against an opponent who was physically struggling. Tien closed out the third round in five sets against Jakub Mensik (6-3, 1-6, 6-7(2), 6-3, 6-4), after going down two sets to one, finishing deep into the night.
At twenty you recover fast, and twenty is the same age at which he reached the quarterfinals in Melbourne this year. But his game plan against a hitter requires quick feet in the third and fourth sets, and that's the part of the tank a fifth set drains first.
On the other side, there's the context of the season. Khachanov had lost all three hard-court matches he played after the third round of Wimbledon, and this is only his second US Open round of 16 since the 2022 semifinal. Ten good days don't erase eight months of inconsistent form, and when his serve drops off, the rest of his game doesn't cover for it.
The prediction, and what would disprove it
Tien is favored, but by a narrow margin: he wins if he consistently stretches points past four shots and if Khachanov's first-serve percentage drops below 60% in at least two of four sets. Serving to avoid the rally is the condition Tien has to take away from him.
The prediction falls apart if Khachanov stays above 65% first serves for two consecutive sets. In that case the American ends up serving under pressure every time with the least reliable shot in his repertoire, and the five sets from the third round start to weigh on him instead of helping him.
