It could be said that someone finally made Novak Djokovic sweat in this year’s U.S. Open. The beneficiary of two retirements and a walkover in rolling downhill toward the final, Djokovic on Friday at least encountered a semi-competitive semifinal against Gael Monfils.

It also should be noted that perspiration was no option for anyone in the humid, 90-degree-plus heat at sweltering Arthur Ashe Stadium. And, apart from Monfils’ third-set flurry, Djokovic’s biggest problem was the squandering of 12 break-point opportunities during the 6-3, 6-2, 3-6, 6-2 victory.

“We both struggled toward the end of the third and beginning of the fourth,” Djo kovic said. “Long rallies. Tense moments, obviously. Physically, we both felt the humidity and the tough conditions. Just very glad to overcome that.”

Djokovic built a 5-0 lead in the first set and, through the first two sets, continually drove Monfils far behind the baseline, setting himself up halfway to the net for put-away shots. When Djokovic broke Monfils’ serve to start the third, the lack of a Monfils challenge had the demanding Ashe crowd loudly booing.

“For sure, people were expecting a tougher battle,” Monfils said. “And then maybe they listen to commentary [of former champion John McEnroe] and say I’m unprofessional, I’m poor, whatever.”

His answer was to extend a few rallies with athletic gets of Djokovic drop shots, volleys and lobs. He began to lure Djokovic into overhitting by taking pace off his shots.

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“I was completely caught off guard when he just stood there and chipped the ball back and didn’t do much,” Djokovic said. “But that’s Gael. He loves to come up with a variety in his game.”

Monfils staved off three break points in the fourth set’s second game, then got a backhand winner that barely hopped over the net — prompting him to bend and kiss the top of the net — and the show was on.

Only briefly, though. Djokovic broke serve in the fourth, sixth and eighth games to conclude the proceedings.

“I’m competing,” Monfils insisted. “The change is guts, you know, against the world No. 1. Five-0, OK, I show you that I play the non-academic way. But the guy is too good. He’s still Novak.”

So Djokovic, the 12-time major-tournament champion from Serbia, is back in the Open title match for a seventh time and reached his seventh Grand Slam final in the past eight events.

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Until Friday, Djokovic, 29, had played only nine sets and 84 games in the first 11 days of the Open, record inactivity for a Slam semifinalist in the open era dating to 1968. Though Monfils, the No. 10 seed, also was relatively well rested by having sailed through five straight-set victories, he nevertheless was facing some daunting history — not to mention the dominant Djokovic, against whom he now is 0-13.

In the last 25 years, only 10 players — before the 30-year-old Monfils — reached the Open semis without dropping a set, and eight of the previous nine failed to win the title. Monfils makes nine of 10.