WHAT HAPPENED: Kei Nishikori and Gael Monfils, both former Top-10 players, were putting on a show worthy of Thursday's night session in Louis Armstrong Stadium when bad luck – or rather, a volley – struck Monfils’ right wrist, causing the Frenchman to retire in the second set with Nishikori leading, 6-2, 5-4.

Nishikori, the No. 21 seed, ran away with the first set, 6-2, but Monfils immediately made it a match in the second. He broke Nishikori in the opening game with a crosscourt forehand missile that caused the crowd to erupt. After an easy Monfils hold, he and Nishikori both played their best tennis, skidding to dig out shots and retrieving overheads to extend points. Serving at 1-4, Nishikori saved three break points in the longest game of the match.

Then, the shot that spoiled the fun opened the next game.

With both players at net, Nishikori’s reflex volley hit Monfils’ right wrist. The Frenchman called for a trainer, then resumed play. He dropped serve by framing a backhand, a startling reversal of form. After an easy hold by Nishikori evened the score at 4-4, Monfils started bailing out early in points on his service game by going for drop shots early in the rally. He retired after dropping serve.

"Well, unfortunately it finish for him," said Nishikori after the match. "We always battle. Play great match all the time. So he's, like, my rival. It's always fun to play against him."

WHAT IT MEANS: Nishikori next meets his first seeded opponent, No. 13 Diego Schwartzman, in a third-round match. Schwartzman advanced today with a fairly routine four-set win over newcomer Jaume Munar of Spain. Both Nishikori and Schwartzman are among the quickest players on the ATP World Tour and had breakout performances in the past on the courts in Queens, with Nishikori reaching his lone Grand Slam final here in 2014 and Schwartzman upsetting 2014 champ Marin Cilic last year in a run to the quarterfinals. Nishikori is 2-0 against the younger Schwartzman; both matches last year went the distance on clay.

MATCH  POINT: Monfils was going for his 100th Grand Slam match win Thursday night.