Jannik Sinner, the reigning world number one and defending Cincinnati Open champion, delivered another memorable performance under the lights on August 12, 2025, defeating Canada’s Gabriel Diallo 6-2, 7-6(6) to secure a place in the tournament’s last 16. But while the scoreboard showed a straight-sets victory, Sinner’s reaction after the match revealed a relentless drive that’s become his trademark—and perhaps the secret behind his meteoric rise in men’s tennis.
The Italian star, just 23 years old, didn’t head for the showers or the press room after dispatching Diallo. Instead, at 10pm, he marched straight to the practice courts, racket in hand, and put himself through a grueling session of roughly 100 serves. Why the late-night grind? Despite his win, Sinner was openly dissatisfied with his serving, a vulnerability that had crept into his game against the towering Canadian.
“I feel like today was a very difficult day at the office,” Sinner admitted in his post-match interview, his candor as striking as his forehand. “He was serving very very well, especially in the second set. Against big servers you always have to find the right balance at the back of the court. Today, I struggled a bit at times. But still very happy. I need these tough matches to get used to very difficult situations.”
That elite mentality—the willingness to scrutinize even a winning performance—has propelled Sinner into an exclusive club. With his victory over Diallo, Sinner became just the fifth player in tennis history to notch 23 consecutive wins on hard courts, joining legends Novak Djokovic, Rafael Nadal, Sir Andy Murray, and Roger Federer. The last to achieve such a streak was Djokovic, back in 2020.
Yet, the numbers from Sinner’s serve against Diallo painted a mixed picture. Compared to his previous round against Daniel Elahi Galan, Sinner’s first serve percentage dipped notably from 64% to just 50%. He fired 6 aces in both matches, but his double faults crept up from 3 to 5. His first serve win percentage also dropped from a staggering 96% to 81%, while his second serve win percentage ticked up slightly from 62% to 65%. Perhaps most tellingly, he was broken once by Diallo, after holding serve throughout his earlier Cincinnati Open rounds.
It’s no wonder Sinner was eager to iron out the kinks. “I’m very happy this happened before a Grand Slam. Hopefully, these situations I can keep for the main goal here in U.S.,” he said, referencing the fast-approaching US Open, where he’ll look to defend his title after last year’s historic run.
But Sinner’s self-critique wasn’t all doom and gloom. “I’m very happy. These matches can go, at least in a third set, if you don’t play well or serve well in important moments, you can lose matches like this. I’m happy about today. Can I do things better? Yes. But not every day is the same. So I’m very very happy.” His balanced perspective—demanding but not despairing—has endeared him to fans and pundits alike.
Diallo, for his part, made Sinner work hard, especially in the second set. The Canadian’s serve was on fire, and Sinner had to save a set point in the tie-break before finally sealing the match. “He was serving very very well, especially in the second set,” Sinner reiterated, acknowledging the challenge posed by the up-and-coming Canadian.
With the win, Sinner advances to face France’s Adrian Mannarino in the last 16. Mannarino, a savvy left-hander and former top 20 player, earned his shot at Sinner by coming from behind to defeat American Tommy Paul 5-7, 6-3, 6-4. Their upcoming clash promises intrigue, but history is firmly on Sinner’s side. The Italian has won all three of their previous meetings on hard courts, dropping just one set in the process. Their head-to-head includes victories at the 2020 Sofia Open (6-3, 7-5), the 2022 Canadian Open (2-6, 6-4, 6-2), and the 2023 Indian Wells (7-6(7), 6-4).
“Sinner has every reason to be feeling confident about playing the Frenchman,” noted one analyst, pointing to Sinner’s dominance in their past encounters and his current form. Still, Mannarino is no pushover—his recent win over Paul showcased his trademark grit and tactical acumen.
Should Sinner get past Mannarino, a potential semifinal showdown with Taylor Fritz looms on the horizon. Fritz, the American number one, has been in strong form this season and would relish the chance to test himself against the world’s best on home soil. But as Sinner’s own experience against Diallo proved, no match can be taken for granted, especially in the pressure-cooker environment of a Masters 1000 event.
Sinner’s journey at this year’s Cincinnati Open is also colored by the tournament’s recent refurbishment and the weight of history. He captured the title here for the first time just last year, a breakthrough that set the stage for his subsequent triumph at the US Open. Now, as the defending champion, he’s shouldering new expectations but seems determined to rise to the occasion.
His approach—laser-focused, relentlessly self-improving, and unafraid to put in extra hours when others might rest—has drawn comparisons to the very legends he now stands alongside in the record books. It’s a mentality echoed by his rival Carlos Alcaraz, who was also seen hitting the practice courts after his own victory in Cincinnati, a sign of the new era’s hunger and professionalism.
As the action continues, all eyes will be on Sinner’s serve in his next match. Will the late-night practice pay off? Can he maintain his hard-court streak and extend his dominance over Mannarino? With the US Open looming, every match is a chance to fine-tune, to test nerves, and, perhaps, to make more history.
For now, Sinner’s campaign in Cincinnati is alive and brimming with possibility. His work ethic, resilience, and ever-growing list of achievements have made him one of the sport’s most compelling figures. As the tournament heads into its crucial stages, fans and foes alike are left wondering: how much higher can Jannik Sinner climb?
