Brimming with confidence and a one-set lead, the Roland Garros crowd whipping into a frenzy behind him, Tsitsipas began smacking the ball with abandon, moving a seemingly hobbled Djokovic backward and forward and going to the net to finish off points. He broke Djokovic’s serve in the first game, then, leading, 4-2, laced a forehand down the line and forced Djokovic into yet another error to get his second break of serve.

On the changeover, Djokovic smothered his face with his towel, exhibiting a kind of hopelessness and despondence he rarely does. A game later, Tsitsipas had a two-set lead and the match was his to lose.

It is one thing to win two sets in a Grand Slam match. It is another thing entirely to win the third one against a player who is on the verge of winning as many Grand Slam singles titles as any man who has ever picked up a racket.

Leading, 2-1, in the third set, Djokovic started jumping on Tsitsipas’s serve for the first time in nearly an hour, pushing him back into the court and moving him from side to side. His shots started landing in spots that left Tsitsipas totally out of position once he caught up to them.

It was as though Djokovic had finally figured out that if he didn’t have the strength to swing an ax he could still use a scalpel. His serve often struggled to get to 100 miles an hour. And at the same time, the precision that had been with Tsitsipas for much of the afternoon was gone.

“I felt like he could read my game better,” Tsitsipas said.

On the fifth break point of the game, Djokovic sent his return deep to Tsitsipas’s backhand, and Tsitsipas sent it back to the middle of the doubles alley. Djokovic had a lifeline, and five games later he had the third set. Tsitsipas called for a trainer to stretch his hips.

Djokovic did not stop there.

The fourth set resembled target practice, a series of surgical strikes from Djokovic that resulted in so many blasts long and wide, or easy balls to the middle of the court, from Tsitsipas. A masterly Djokovic backhand drop shot from behind the baseline gave Djokovic a second service break, and a 3-0 lead. Tsitsipas had to battle just to keep the set from being embarrassing.