WHAT HAPPENED: In a nervy, four-hour thriller of spectacular ball-striking and gutsy net closes that ended in an extraordinary fifth-set tiebreak, the surging Frenchman, 22-year-old Lucas Pouille, upset the fourth seed and two-time US Open champion Rafael Nadal, 6-1, 2-6, 6-4, 3-6, 7-6.

In the final set, Nadal held a 4-2 lead and appeared to be on the verge of a titanic victory, when a couple of sudden, crucial errors entered his game. The Spaniard lost serve and allowed Pouille to creep back into the match.

In the final-set tiebreak, Pouille held a seemingly insurmountable 6-3 lead, with three match points on his racket. A gritty Nadal battled back to level the breaker at 6-all as the excitement within Arthur Ashe Stadium reached a breaking point.

On an afternoon in which both players hit numerous incredible shots from every part of the court, Nadal missed a sitter, netting a forehand instead of crunching it into the open court.

On the next point, with Nadal serving to survive, Pouille showed no hesitation. After a long, tense rally, he pummeled a forehand within inches of the sideline to win the biggest match of his life, and the undisputed match of the tournament.

“My first match on Ashe against Rafa: I couldn’t dream better than this,” exclaimed Pouille on court after his stunning victory.

Pouille did nearly everything well. He was powerful but supremely controlled. He hit 59 winners, picking perfect spots to be offensive and unloading off of both wings. He rallied patiently with Nadal. When the Spaniard upped his game after a first-set rout, and again in the fourth and fifth sets, the Frenchman played adept defense, too.

Dressed in bright pink and neon yellow, Lucas Pouille pulled off the biggest shocker of the US Open.

WHAT IT MEANS: Pouille, the 24th seed – who has now won three five-setters in four rounds in Flushing Meadows – advances to his second career quarterfinal in a major (he also reached the quarters at Wimbledon earlier this year). Pouille joins compatriots Gael Monfils and Jo-Wilfried Tsonga in the quarterfinals here and will meet Monfils next.

The Frenchman has had a breakout year, surging in the rankings. He reached his first career tour final, in Bucharest, and made the semifinal at the Masters event in Rome.

Rafael Nadal, the fourth seed whose 2016 season has been truncated by a wrist injury that caused him to pull out of Roland Garros and miss Wimbledon entirely, only returned to competitive play at the Rio Olympics in late summer (where he won a gold medal in doubles). Nadal has not reached a Slam quarterfinal since the 2015 French Open.

THE QUESTION: Will Pouille have anything left in the tank after three five-set matches against tenth seed Monfils?