ATP Tour
Pegula and Keys marvel at Sinner’s serve surge after Isner inspiration
Pegula and Keys praised Sinner’s serve, with Keys revealing his Isner-inspired changes.
Jessica Pegula and Madison Keys have highlighted just how much Jannik Sinner’s serve has evolved, with both WTA players saying the improvement is so dramatic that it “doesn’t make sense.” Keys also pointed to a surprising source behind the world No 1’s progress: John Isner.
Sinner has been the defining player of the 2026 season, putting together a 44-3 record while collecting five Masters 1000 titles. He has also reached the semi-finals of the Australian Open and successfully defended his Wimbledon title, and his form has left him 1410 points clear of world No 2 Alexander Zverev in the ATP Live Race. That position has already assured him of a place at the season-ending Nitto ATP Finals.
His lone major setback came at the French Open, where he was upset in the second round by Juan Manuel Cerundolo in difficult conditions. Even so, the overall progress in his game has been easy to track, especially on serve.
The numbers underline that change. Over the past 52 weeks on the ATP Tour, Sinner’s service rating is 302.4, behind only Reilly Opelka and ahead of players such as Ben Shelton and Taylor Fritz. He also leads the tour in service games won at 92.9 percent and first-serve points won at 80.9 percent.
Speaking on their “The Player’s Box” podcast, Pegula said: “His serve is so good, one of the best, most improved shots,” before adding: “They should give awards to Sinner’s serve. His serve is a joke. His wide serve on the ad side is insane.
“And every time I watch him, I’m like, ‘Ooh, like I know that’s his favourite serve and it’s like kind of low percentage.’ Like you always think, ‘Oh, there’s no way he’s going for it again.’ Just hits an ace every time.
“I don’t understand. Like how did your serve get so much better?”
Keys explained that Darren Cahill had urged Sinner to study Isner’s motion and copy elements of it. She said: “I thought it was pretty crazy because I think I heard Darren talking about it when he first started with Jannik and one of the big things was like we need to improve your serve,” added the American.
“That’s your thing. Basically, pick someone to watch and then just try to copy their serve. And he watched John Isner and was just like, ‘Okay, got it.’
“And then it’s crazy that when you’re at the top of the game or you’re one of the three at the top of the game to keep improving and being willing to change things when you’re holding 87 consecutive times against people [Alexander Zverev] and someone comes to you like, ‘Yeah, we should make a tweak.’
“The fact that he’s like, ‘Yeah, okay. No problem.’”
Isner later reacted on Instagram with a joke of his own: “Serving like me with an actual baseline game is a decent combo.”
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Zverev closes in on Sinner as the ATP ranking battle intensifies
Zverev has cut into Sinner’s lead, and the points race is now tightly balanced.
Jannik Sinner had to view the outcome from afar as Alexander Zverev beat Ben Shelton in the US Open final to secure a second Grand Slam title.
Zverev has made the most of injuries to Carlos Alcaraz and Sinner during the season, adding both Roland Garros and the US Open to his resume. That run has left the race at the top of the ATP Tour rankings finely poised, with only 1810 points separating Zverev and Sinner.
The German now has a clear opportunity to challenge for the No. 1 spot before the year is out, while Sinner faces a demanding return to the tour. The Italian is expected back at the China Open, which starts on September 30th, but that comeback arrives after a long absence from competition. He has not played since Wimbledon in July, so regaining rhythm will be part of the challenge.
The pressure on Sinner goes beyond form. Between now and the end of the 2026 season, he is defending 3,550 ranking points. Much of that total comes from a strong run at this stage last year, when he won the China Open, the Vienna Open, the Paris Masters, and the ATP Finals.
That means he will need to reproduce those results to protect his points and hold off Zverev in the closing months of the season. The one event where he will not carry that same burden is the Shanghai Masters, scheduled for October 7th to 18th, because he was defeated in the round of 32 there in 2025 by Tallon Griekspoor after fatigue set in.
There are still unknowns around Sinner’s physical condition, and the calendar offers little room for adjustment. Even so, he has already shown he can beat the best without much match play. He won Wimbledon without a warm-up tournament on grass, defeating Novak Djokovic, Zverev, and Jenson Brooksby along the way.
Zverev, by contrast, enters the run-in with only 1,040 points to defend. He did not win a title during this stretch in 2025, giving him a strong opening to collect points and keep pressing for the top of the ATP Tour.
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Zverev’s serving routine draws scrutiny after US Open title run
Zverev’s US Open win has sparked debate over his serve routine and its impact.
Alexander Zverev emerged as a deserving US Open champion this year, yet his routine between first and second serves has become a talking point at the Grand Slam.
Several players and observers have taken issue with the amount of time the German spends bouncing the ball before serving. Over the course of his seven matches in New York, Zverev reportedly spent two and a half hours bouncing the ball, a detail that especially irritated his final two opponents, Karen Khachanov and Ben Shelton.
“It doesn’t bother just me. It makes a lot of players uncomfortable because he takes so much time,” said Khachanov about Zverev’s serving routine.
Shelton also argued that the issue should be addressed through a rule designed to stop players, including Zverev, from taking excessive time between serves.
Not everyone sees the matter the same way. Mark Petchey defended Zverev’s motion in a social media post, pointing instead to other aspects of the German’s game. He wrote: “I love the fact that Alexander Zverev plays within the rules. One of the very few players who walks around the net after the first game and at the changeovers in tiebreaks.
“Serves within 25 seconds. The ball bouncing isn’t the issue. It’s the 70% plus 1st serves in that’s the problem for everyone. Overcome some absolutely brutal heartbreaking losses. Granite mentality and work ethic. Double Major winner in a season.”
Petchey then suggested that Zverev’s second Grand Slam title has placed him firmly on a Hall of Fame path, saying: “Hall of Fame career incoming,” said Petchey. “Congratulations Sascha.”
Zverev was asked about the bouncing during a post-match press conference at the US Open and said: “I have no idea why. I don’t do it on purpose,” said the German when asked about his potential timewasting. “I saw the statistic that I’ve bounced the ball around 12,000 times or something like that. It’s pretty funny. I’m not counting them in my head or trying to reach a specific number.”
He was due to feature in Davis Cup action for Germany against Croatia on September 18th, but he did not confirm his participation after winning the title. “I really, really would like to play in the Davis Cup,” said Zverev. “Everyone around me is trying to talk me out of it. But I will decide that tomorrow.”
Zverev’s last Davis Cup appearance for Germany came at last year’s finals, when they were eliminated in the semi finals by Spain.
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Sinner’s No. 1 lead under pressure after Zverev’s US Open surge
Zverev’s US Open win has closed the gap on Sinner, who now faces a tense ranking battle.
Alexander Zverev’s US Open title run has tightened the race at the top of the ATP Tour rankings, leaving Jannik Sinner with a much smaller cushion than before. Sinner did not compete at the US Open, while Zverev made full use of the opportunity, defeating Ben Shelton, Karen Khachanov, and Botic van de Zandschulp on his way to the trophy.
The German’s second Grand Slam crown has lifted him to within 1,810 ranking points of Sinner as the season moves into its decisive phase. That gap may yet shrink further, especially after Sinner confirmed his place in the Vienna Open, the ATP 500 indoor event scheduled for October 24 to November 1.
Sinner is the defending champion in Vienna, and his decision to return there underlines how important ranking points have become in the battle to keep hold of world No. 1. He is defending 3,550 points between now and the end of the season, while Zverev has only 1,040 points to defend.
Sinner’s recent history in the closing weeks of the season supports his position. Last year he won the China Open, the Vienna Open, the Paris Masters, and the ATP Finals, showing his strength on indoor hard courts. Even so, there are concerns around his current condition. He has not played since Wimbledon because of a knee injury, and that absence could make it harder for him to immediately hit top gear again on the ATP Tour.
His schedule also includes the China Open and the Shanghai Masters, two tournaments that are known for difficult heat conditions. Sinner has previously struggled in the heat and came close to retiring at the Shanghai Masters last year before losing to Tallon Griekspoor.
Zverev, meanwhile, is producing some of the best tennis of his career. His confidence, built on a two-time Grand Slam-winning season, could carry him through the rest of the year. He has also been a strong performer on hard courts, having won the Vienna Open, the ATP Finals, and the Chengdu Open on this surface in the past. With both men under pressure, the fight for No. 1 looks set to stay close.
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