As any player will attest, some losses sting more than others but it’s what you learn from them that counts. For Novak Djokovic, a four-set defeat to Kei Nishikori in the 2014 US Open semi-finals did not so much spark a learning curve as a learning leap.

Defeat at the time sent Nishikori through to his lone Grand Slam final to date. It also handed him a 2-1 FedEx ATP Head2Head edge over the Serbian. How quickly those tides turned. Djokovic has never lost to the Japanese player since – that’s 13 straight victories now.

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Nadal vs Del Potro | Djokovic vs Nishikori

As the No. 6 seed and two-time US Open champion admitted ahead of their semi-final on Friday, there was something about Nishikori’s game that flicked his competitive switch from the get-go.

“We had some matches where I won in straight sets, but we had a lot of matches, especially on clay courts, where it went the distance, where a couple of points really decided the winner,” Djokovic said. “In Rome we played a couple matches there. This year he was close to being the winner of that match.

“I have a very good head-to-head score against him. But because he plays so fast, he makes me more alert from the first point because I know I have to be at my best in order to compete with him from the baseline.”

Djokovic has beaten him three times this year already, including the quarter-finals en route to his fourth Wimbledon trophy. It was a trophy run that restored his confidence and carried into the North American hard-court summer, where he went on to complete the Career Golden Masters in Cincinnati. After seeing off the dogged challenge of Roger Federer’s conqueror, John Millman, to reach the semi-finals, it became clear Djokovic was again beginning to peak at the pointy end of the tournament.

Having missed last year’s US Open and this year’s Australian Open due to a right wrist injury, 2018 has been a season of rebuilding for former World No. 4, Nishikori. He avenged his 2014 US Open final defeat to Marin Cilic on Wednesday, denying the No. 7 seed in five sets. 

The 28-year-old said he was playing without the pressure to maintain a Top 10 ranking and it was showing. He might do well now to dig up footage of his semi-final victory over Djokovic from four years ago.

“Yeah, I forgot about it,” he grinned. “I always have good memories here. It was a tough battle against Novak. For sure, it’s gonna give me good confidence, even though I [can’t] remember. Maybe I will try to watch the match again, if he wins, and get more confidence.”

In a showdown between two of the ATP World Tour’s best baseline movers, Nishikori would not shy away from what made this match-up so difficult for him.  

“Well, he’s very solid from baseline,” the No. 21 seed said. “He doesn’t have many weakness. He has a great backhand and forehand, too. He can be aggressive, and serve, he got better, too. I will say everything.” 

Mike Bryan assures his brother Bob Bryan his job is safe once he returns to the world’s most successful doubles partnership from a hip injury. In the meantime, Jack Sock is proving a more than sufficient substitute.

Mike Bryan and Sock won through to their second straight Grand Slam final on Thursday, to extend their unbeaten run in the majors to 11 matches. And it will be a battle of the past two Wimbledon champions when the Americans meet No. 7 seed Marcelo Melo and Lukasz Kubot in the final.

Bryan/Sock prevailed with a dramatic 6-2, 6-7(1), 6-4 semi-final victory over fifth seeds Robert Farah and Juan Sebastian Cabal on Thursday. The match could have been a relatively routine 6-2, 6-4 result had Bryan closed it out with match point on his serve in the second set. 

The Colombian duo had already ended Bryan/Bryan’s run in the Australian Open semi-finals in January and a second straight hard-court Grand Slam final was suddenly on the cards again when they forced a deciding set.

The American No. 3 seeds, however, made no mistake of it second time around. They converted on match point No. 2 with a break of serve in the final game of the match.

“Obviously we could have won that thing in straights [sets]. We could have won this 45 minutes ago but it’s a good mental test,” Bryan said. “Those guys are really good fighters. That’s my bad. I should have served it out.”

At 40, Bryan will be bidding for his 18th Grand Slam title, his sixth at the US Open. A win over the Polish-Brazilian pair in the final would break his tie with John Newcombe for most major doubles titles. 

“I’m just having a blast. This is my 24th [US] Open,” Bryan said. “Still doing it and really savouring these moments. Who knows? It could be one of my last finals here. Bob, keep rehabbing that hip. Jack’s done pretty good filling in for you.”

At Wimbledon, Bryan/Sock pulled through three five-set matches to clinch their first title together. Sock was asked whether it was better heading into the US Open final having pulled through a long match or to have done it easily.

“I think everyone wants to hear ‘dig deep’ but I’d rather be off the court faster, to be honest,” Sock laughed. “We spent a lot of time on court, a lot of wear and tear on the body so obviously any time you can get through in straights [sets] the better. It’s been a long season. 

“But as [Mike] alluded to, it’s almost a little bit sweeter feeling if you maybe have chances, not get it, but staying mentally tough and pulling through again.”

After finishing 2017 as the No. 1 doubles team in the world, Kubot/Melo contested their first Grand Slam semi-final of the season when they came up against alternates Radu Albot and Malek Jaziri on Thursday. The seventh seeds had lost five of the past seven matches heading into the US Open but were turning their season around in New York.

Kubot/Melo booked their place in their first final since claiming the Gerry Weber Open in Halle with a 7-6(3), 3-6, 6-3 victory over the Moldovan/Tunisian pair. They will look to extend an unbeaten 2-0 record in finals this season when they meet the Bryan/Sock partnership for the first time.

He grew up in Brisbane, so knows a thing or two about humidity. But on Wednesday night, the hot conditions at the US Open got too much for John Millman.

“I’m not normally like the biggest sweater,” said Millman. “But I was really sweating…”

With temperatures at a relatively cool 70ºF, but humidity above 80 per cent, the Australian was drenched in perspiration as he approached Novak Djokovic at the net at 2-2 in the second set.

“Can I go change my clothes now?” Millman asked Djokovic. “They are saying I can only change now.”

It was a win-win for both. Djokovic smiled, and could be heard saying, “I can take a little rest.” The Serbian soon took off his shirt at his courtside bench.

The chair umpire agreed, invoking the ‘Equipment Out of Adjustment’ provision in the ITF Duties and Procedures for Officials, due to Millman’s excessive sweating and the moisture it was leaving on the court.

“It was a tricky one coming off,” said Millman. “I didn’t really want to come off. Novak was making me run a bit too much, though… I had to change!”

Two-time former US Open champion Djokovic believes it’s the toughest US Open he has contested in the past decade.

The Serbian later admitted, “I personally have never sweat as much as I have here. [It’s] incredible. I have to take at least 10 shirts for every match. It’s literally after two games you’re soaking.”

A similar situation occurred on Tuesday night, between the fourth and fifth sets of Rafael Nadal and Dominic Thiem quarter-final, when Thiem was allowed to get new shoes from the locker room.

Four years ago in Flushing Meadows, Kei Nishikori earned perhaps the biggest win of his career, defeating top seed Novak Djokovic in the semi-finals to reach his first Grand Slam final.

“I forgot about it,” Nishikori said on Wednesday, smiling. “I always have good memories here. It was a tough battle against Novak. Yeah, for sure it’s going to give me good confidence, even though I didn’t remember. Maybe I will try to watch the match again, if he wins, and get more confidence.”

In the championship match, which lasted just one hour and 54 minutes, Marin Cilic cruised past the Japanese to lift his maiden major trophy. But now, it’s time to press rewind. Nishikori will try to upset Djokovic in another US Open semi-final. Will the script remain the same?

First thing’s first — the circumstances are different. Nishikori is no longer on the rise, but on the mend. The 28-year-old missed this tournament last year due to a right wrist injury, and he’d start his 2018 campaign by playing two ATP Challenger Tour events.

But Nishikori is not satisfied having reached one major final and climbing as high as No. 4 in the ATP Rankings. While he’s not putting as much pressure on himself before his injury, he is ambitious. Nishikori doesn’t want to settle for making the semi-finals at the USTA Billie Jean King National Tennis Center.

ESPN analyst Brad Gilbert worked with the Japanese from December of 2010 through the 2011 season, and he says he was a little bit surprised when he asked Nishikori about his goals seven years ago.

“I wasn’t sure. But it was to be Top 3 in the world, to win Slams, to compete in Slams,” Gilbert said. “Okay, sometimes you’re not sure and your people say it, but you don’t really believe it. But I think he really believed in it and expected it.”

And perhaps it is that belief that has aided his return to form. First it was a runner-up showing in Monte-Carlo, then his first quarter-final at Wimbledon, and now, after avenging the Cilic loss by ousting the Croatian on Wednesday, he has earned a spot in the US Open semi-finals.

“It’s almost like he willed that win. It was perseverance. It wasn’t pretty. It was brilliant at some times. But the biggest thing in tennis, they said the four most valuable words: game, set, match, Nishikori,” Gilbert said of Nishikori’s victory against Cilic. “That match had like seven, if it was wrestling, it would be reversals. He found a way to win the last point and that’s the only thing that matters in these majors.”

Nishikori didn’t have the best preparation for the US Open, losing three of four matches heading into the final Grand Slam of the year. But that hasn’t stopped him from battling match-in and match-out and, in the crucial moments, being unafraid of taking control and seizing the moment.

“I felt once we were getting into the rallies he was slightly more consistent, and he had in, most of the rallies — not most of them, but maybe 60 per cent of the rallies — that he was the one that was dictating and creating chances,” Cilic said. “I felt that once he had the ball in the middle of the court, he was controlling and playing well what he’s doing usually well.

“He’s playing really well. He’s in the semis, and with these kind of conditions, I think he dealt with it quite good today… I think for him is definitely good challenge coming back to the semis and creating another opportunity. I felt that he was hitting the ball really clean, really well, as he usually does.”

And the scary thing for the remaining field, is that Nishikori did not feel he was at his best against Cilic, who had made two of the past five Slam finals. “It wasn’t easy, and I didn’t feel like I was playing [my] best tennis today, but [I] fought through somehow and [that] gives me big confidence playing semis [in the] next round,” he said.

Nishikori has shown an even higher level this tournament, which is impressive considering he defeated Cilic. The No. 21 seed dominated veteran Philipp Kohlschreiber in the fourth round, a match that Gilbert commentated on.

“I thought he played excellent. He played great in that match,” Gilbert said. “The amazing thing about tennis is sometimes you don’t have to be great to win. Sometimes you can just be ordinary, but you’ve got to win. I don’t think he played that well today, but more importantly, sometimes you can play really well and lose. They said game, set, match, Nishikori. He’s moving on.“

There’s no doubting that Nishikori’s wrist injury was a significant hurdle to leap over. Missing the end of the 2017 season following Montreal, he’d eventually drop to World No. 39 this April, his lowest placement in the rankings since he was 21 years old. But now, Nishikori is working back toward his peak again and into contention for a spot at the Nitto ATP Finals in November.

“In tennis, if you don’t get better, you get worse. And he’s been getting better. He’s had lots of injuries to deal with. But all you can do sometimes is ask yourself and put yourself in the position,” Gilbert said. “He’s put himself in position and now… he’s just got to play the opponent and not the situation.”

All Nishikori has to do is check out video of the last time he played Djokovic in Arthur Ashe Stadium. While he may or may not remember it, the film doesn’t lie: Nishikori’s done it before, and there’s no reason he can’t do it again.