ALL ENGLISH CLUB, London – Just in time for the busiest part of Wimbledon, London is heating up.
Jannik Sinner, the reigning men’s champion and world number one who has shown a penchant for melting in hot weather, is likely to play a familiar opponent in the semi-finals: 24-time Grand Slam champion Novak Djokovic could be waiting for the 24-year-old Sinner under a bright 87-degree sun on Friday afternoon.
Ahead of the tournament, Italy’s Sinner said he and his team had committed to training in hot weather to adapt their bodies to a schedule that is getting hotter every year.
But this Wimbledon, Sinner’s problems have so far been more prosaic, and it has been easier to find a solution. His main game was out of rhythm. His delivery is a vicious metronome that keeps him on the straight and narrow.
Once again, against the dangerous Jan-Lennard Struff of Germany, who combines a loud serve with a penchant for moving forward and attacking at will, the Italian’s serve was the key to victory.
In a 7-5, 7-6(4), 6-3 victory, Sinner served 16 aces to Struff’s 12. He completed 65 percent of his first serves and won 84 percent of those points, and crucially, he still won them when Struff did return the ball. Sinner scored 69 percent of the first-serve points that Struff scored through the net and between the lines; when Sinner returned the first serve, he won the point rather than losing it.
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Sinner declared his serve after a fourth-round win over Shintaro Mochizuki, the world No. 151 from Japan. Sinner won the first set comfortably in 33 minutes, but the match seemed to get tighter in the second set when it came to the tiebreaker. If Mochizuki had a chance to fight, this was it.
Mochizuki never really stood a chance, even if at first glance it looked like Sinner was in for another long day after taking five sets against Serbia’s Miomir Kecmanovic in the first round.
In the second set against Mochizuki, Sinner completed more than 70 percent of his first serves and won 24 of 28 points in the process. He made 10 aces. In total, he scored 38 points on his serve, and in 17 of them he did not have to hit a second blow.
He scored just three of the seven points in the tiebreaker, which he won 7–0. Ace. A shot to the T that put Mochizuki on his back foot, then hit a shot on goal that Mochizuki sent into the net.
“At times I thought I served well, especially in the big moments today,” Sinner said at his press conference. “It also helped me be a little freer in the return games.”
That is Sinner’s plan for the remaining two weeks of Wimbledon if he is to lift the trophy for a second year in a row. He is not the same player he was at the beginning of the clay-court season, when he won three tournaments in a row – the Monte Carlo Masters, the Madrid Open and the Italian Open. Before them, he won the BNP Paribas Open at Indian Wells and the Miami Open, but even that dominant run on the hard court showed signs of slipping.
Sinner then used his dominance on serve to compensate for shakyness in his base game, especially on the forehand. Essentially, nothing has gotten worse, but in tennis, a sport with such high returns, small changes in winning percentage, especially in the most common scoring types, can have a big impact.
Entering 2026, his pitching has given him a one percent increase in his win average on points that last between zero and four shots. That doesn’t sound like much. But this is the most common problem in tennis, and with Sinner’s winning percentage on points per nine shots falling four percentage points below average, the one percentage point shift made up for it enough to keep winning.
The most devastating version of Sinner, who crushes opponents from the back of the court, displays masterful touch when he comes forward, and still serves like a metronome, may yet emerge.
After cramping and cramping in the third round of the French Open against Juan Manuel Cerundolo, the world number 54 at the time, Sinner took a well-deserved rest. He didn’t play a competitive match until Wimbledon, where he was understandably rusty against Kecmanovic.
This is an era where using a killer as a pressure release valve has never been a more valuable weapon in both the men’s and women’s game. Players are so athletic, and so many points can flow from offense to defense and back again, that as long as the rest of a player’s game is stable, an effective serve can become something of a fortress.
This is especially true on grass, where the ball slides, glides and lifts off the court rather than popping up as it does on clay and some hard courts. Four-time Main Event champion Naomi Osaka, who has long struggled on grass, made opponents feel like they couldn’t breathe during the first week as she set the tempo of serving in the women’s tournament, hitting the corners with her 190 mph bombs.
Sinner frustrates opponents who feel powerless to make any progress, no matter how close the score may be at any point in the match, and no matter how much they may feel they can hurt him from the baseline.
“He served well, so I couldn’t break any games,” Mochizuki said after his three-set loss to Sinner. “It cost me a lot.”
This has been coming to Sinner for a long time. Since he switched from a platform stance (feet apart) to a precise stance (feet together) before a moving jump in 2022, Sinner’s serve has become much more than just a starter. This allowed him to jump a couple of inches higher and hit the ball harder.
He was largely responsible for defeating Novak Djokovic in four sets at the 2024 Australian Open, when the best comeback man of the modern era, not named Andre Agassi, failed to save a break point in a five-set match for the first time in his career.
Jannik Sinner’s service helped him through difficult moments. (Cameron Spencer/Getty Images)
More than two years later, Sinner’s delivery has had moments of hiccups. He struggled with this at last summer’s US Open, particularly in the final when he hit just 48 percent of his first serves and was duly knocked off the tee by Carlos Alcaraz.
This Wimbledon was the complete opposite of that. In four matches he has 81 aces. This is equivalent to five “free” games in each match.
His first serve percentage is a reliable 66 percent, and he wins 85 percent of those points. More than half of his successful first serves go unanswered.
A diagram of the contact points his opponents make when they return his serve shows an alarming number of points on the outside or on the edges of the tram tracks. The sinner is not very good to serve the enemy’s body. Only a few balls hit the middle third of the service field.
All this means that no one can get their hopes too high when the pitch does return. Sinner scores 69 percent of those points, the best in the field.
The question now is whether this will be enough to neutralize perhaps Sinner’s biggest enemy this week – the weather. He brushed off a question about the forecast after his win over Mochizuki, saying he didn’t know much about the coming heat, while dismissing the idea that the weather threw him off in Paris immediately after it happened.
In London two weeks ago, he reversed course and admitted he had a problem that needed to be fixed. Against Struff he didn’t need to make amends because his serve was once again the difference maker.
“We are well prepared,” he said. “Whatever happened in the past has already passed. Now we will see if we have found a solution. If not, we will continue to work on the next one.”
He knows how the pressure builds in the final round of a Grand Slam. He said he was ready for it this time.
“There’s definitely more tension. At the same time, I’m very happy where I am at the moment,” he said.