Novak Djokovic prevails where Roger Federer failed but Serb says US Open conditions have to be addressed

Former world No 1 will face Kei Nishikori for a place in the final, but said after his straight-sets victory over Millman that the Arthur Ashe Stadium needs to be looked at to help the players

Where Roger Federer failed, Novak Djokovic prevailed. Forty-eight hours after the 37-year-old Swiss suffered one of the most shocking defeats of his career when he was beaten by John Millman, Djokovic swept aside the Australian on Wednesday to secure his place in the semi-finals of the US Open.

Djokovic, who was won all 11 of the quarter-finals he has played here, beat Millman 6-3, 6-4, 6-4 in two hours and 48 minutes on another sweltering night in Arthur Ashe Stadium.

In Friday’s semi-finals the Wimbledon champion will meet Kei Nishikori, who beat Marin Cilic 2-6, 6-4, 7-6, 4-6, 6-4 to complete a historic double for Japan following Naomi Osaka’s win over Lesia Tsurenko earlier in the afternoon. It will be the first time ever that two Japanese players have played in the semi-finals of the same Grand Slam tournament.

On Monday Millman had ended Federer’s run of 40 consecutive US Open victories over players ranked outside the world’s top 50 as the world No 2 struggled to cope with the stifling heat and humidity.

Djokovic has had his own troubles in the gruelling conditions here, but although there were moments when he again looked distressed the 31-year-old Serb proved a more resilient opponent.

He was helped, no doubt, by one of the most unusual breaks ever seen at a Grand Slam tournament. At 2-2 in the second set Millman was allowed to leave the court to change his kit after the umpire ruled that the playing surface had become dangerous because of the floods of sweat dripping off the 29-year-old Australian.

While Millman was off the court Djokovic sat shirtless in his chair and asked to see the tournament doctor, who gave him a nasal spray. He also appeared to take some salt tablets, though he would not confirm afterwards what they were.

Djokovic said the conditions at this year’s tournament were the toughest he had known in the last 10 years. He said he had never sweated as much and echoed Federer’s comments about a lack of air in the stadium, saying it was a problem the tournament needed to address.

Novak Djokovic compared the Arthur Ashe Stadium to a sauna (EPA)

“Whether it's night or day, we just don't have air down there,” he said. “It feels like a sauna.”

He added: “I personally have never sweated as much as I have here. Incredible. I have to take at least 10 shirts for every match. After two games you're literally soaking. Roger never sweats that much, but look how he was a couple of nights ago.”

Although Djokovic won the first three games, the rallies were hard-fought from the start as Millman kept making his opponent hit the extra ball. The first six games took 42 minutes, but after an hour Djokovic had the first set in the bag.

Millman was sent to change his shirt by the chair umpire (EPA)

Millman held serve from 0-40 down in the opening game of the second set but at 4-4 he double-faulted on break point. Djokovic served out for the second set and again drew first blood in the third, though Millman rallied to level at 3-3. Once again, however, the Australian was broken at 4-4, upon which Djokovic served out to love to complete his victory.

Djokovic paid credit to his opponent. “He makes you miss balls and makes you earn the point,” the Serb said. “He doesn't miss a lot himself. He just runs left, right, gets a lot of balls. Very slow conditions, slow balls, and he just gets a lot of balls back.

The heat once again took its toll on players at the US Open (Getty)

“Tactically, you've got to find the right balance between being patient but constructive in the point, but at the same time be aggressive and take the chance when you have a shorter ball. It's easier said than done, especially in these kind of conditions.”

Millman said he had “left it all out there” but had just come up a little short. “Novak is a champion,” he said. “It's not so easy to play Roger and then to play Novak.

“I think Novak sometimes flies under the radar a little bit, but the guy's won a lot of Grand Slams, he knows how to win them and he knows what this is all about. He's probably one of the most in-form players after winning Wimbledon and Cincinnati coming into this tournament.”

Djokovic managed to win the quarter-final in straight-sets (Getty)

He added: “In these night matches the humidity goes through the roof. It is tricky, but it's the same for both people. You're dripping. But that's no excuse. I'd play in a swimming pool if I got to play a quarter-final every week at a Grand Slam.”

Earlier in the day Nishikori and Cilic had been on court for four hours and eight minutes. The heat rule was once again in operation, giving the players the opportunity to take a 10-minute break off the court after three sets.

Cilic, who has reached two Grand Slam finals in the last 14 months, started strongly and was a set and a break up before Nishikori found his stride. The 28-year-old Japanese won four games in a row to take the second set and won the tie-break at the end of the third 7-5 before Cilic rallied to force a decider.

Kei Nishikori celebrates after defeating Marin Cilic (AFP/Getty)

Nishikori took an early hold of the fifth set by breaking serve in the fourth game, only for Cilic to fight back to 4-4. When the Croatian served at 4-5, however, he went 15-40 down, at which point Nishikori secured his victory with a majestic return forehand winner to avenge his loss to Cilic in the 2014 final here.

Like Djokovic, Nishikori missed the end of last season because of injury. The world No 19, who was at a career-high No 4 three years ago, took time out because of a wrist problem and started off in Challenger tournaments when he made his return in February.

The pair shake hands after an epic five-set quarter-final (Reuters)

His subsequent progress has been impressive. Nishikori reached the final of the Monte Carlo Masters and the fourth round at the French Open before enjoying his best Wimbledon with a run to the quarter-finals. Now he is just one win away from playing in his second final here.

Nishikori was delighted by Osaka’s success. “It's great to see,” he said. “I think she can win a title now, even though it’s a Grand Slam. I feel it is a big chance for her. I am also happy for myself.”