It’s almost cruel the way Novak Djokovic lets opponents win the first set against him and allows them to think they might have a chance to beat him, only for him to then run them ragged and leave them by the wayside.

The No. 1-ranked player in tennis is also the sport’s most finely conditioned, and he went to his proven formula Wednesday night and into Thursday morning in his U.S. Open quarterfinal against No. 6 seed Matteo Berrettini. Playing like a human backboard, returning shots most others would have no hope of reaching, Djokovic came back for a 5-7, 6-2, 6-2, 6-3 victory that put him two wins away from winning a men’s record 21st Grand Slam singles title and becoming the first man to complete a calendar Grand Slam since Rod Laver did so in 1969.

Berrettini, no slouch in terms of conditioning, stayed with Djokovic early but faded in the face of the Serb’s relentless nature and the way Djokovic moved him around to tire him out. There’s no shame in that, just credit to Djokovic for his endurance and unwavering focus. Berrettini also won the first set from Djokovic in the Wimbledon final this year only to lose in four sets, so he has seen this script before.

Djokovic has a 26-match win streak in Grand Slam play. His semifinal opponent will be No. 4 seed Alexander Zverev, who was a 7-6 (6), 6-3, 6-4 winner over unseeded Lloyd Harris on Wednesday. Zverev, the Tokyo Olympic tennis gold medalist, has a 16-match winning streak.

The first set of the three-hour, 27-minute match at Arthur Ashe Stadium featured an epic, 20-point game that went to deuce seven times. Djokovic had two break points but Berrettini managed to hold serve to bring the set level at 3-3. Berrettini had two break points on Djokovic’s serve in the next game but couldn’t cash in, and Djokovic held with an untouchable backhand winner for a 4-3 lead.

Djokovic routinely tries to create a battle of attrition that he knows he can win. He lost the first set in each of his previous two matches — to Kei Nishikori in the third round and Sacramento native Jenson Brooksby in the fourth round — but outlasted and outplayed his opponents in those cases. At least in the early going on Wednesday, Berrettini stayed with him.

A superb forehand passing shot gave Berrettini a break and a 6-5 lead and a chance to serve out the set. He needed four set points to do it, but he won the set when Djokovic hit a forehand long.

Djokovic wasn’t rattled. In the second set he converted his third break point of the match to take a 3-1 lead and consolidated that by holding serve at love to go up 4-1. He had Berrettini down 0-40 in the next game and had five break points but Berrettini came back to hold serve after the game went to deuce five times. He needed that game to prevent Djokovic from running away with the set, and he expended a lot of energy to get it.

Djokovic took that in stride, holding serve at 15 to go up 5-2 and then breaking Berrettini’s serve to close out the second set, 6-2.

Djokovic began the third set by holding serve and then going up a break in Berrettini’s first service game. The Italian began committing more unforced errors than before as Djokovic began committing fewer errors, allowing Djokovic to race off to a 3-0 lead before Berrettini held serve. A comeback, or prolonging the inevitable? Djokovic’s answer was to hold serve and take a 4-1 lead.

With rain in the forecast, the roof was closed and an announcement was made that fans would have to wear masks. Not everyone complied.

Despite a weak second serve, Berrettini held serve in a game that went to deuce six times, cutting Djokovic’s lead to 4-2. Berrettini had a break point in the seventh game but Djokovic held him off and held serve with a forehand winner. Djokovic won the set on his second set point, 6-2.

Djokovic cruised to a 3-0 lead in the fourth set, leaving Berrettini to hope for a miracle. It never materialized.

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