Jannik Sinner capped off a remarkable season, securing his first two Grand Slam titles and finishing the year as world No. 1.

However, as he heads into 2025, the shadow of a potential doping ban still looms over his career.

Though he has managed to quell concerns about a ban derailing his progress, Sinner's mental strength will be tested once again as he faces the daunting task of defending a major title at the Australian Open in January.

"I don't know how I'm going to react or how I'll play," Sinner said after his victory at the ATP Finals in Turin. "I'll prepare as best as I can, like for any event, and we'll see. Tennis is unpredictable – you never know what can happen. So as long as you're mentally in a good place, it'll all be fine."

Raised in the German-speaking town of San Candido in Italy’s Tyrol, near the Austrian border, Sinner spent much of his youth carving up the slopes on skis.

After switching his focus solely to tennis a decade ago at the age of 13, his trajectory has been all upward, with a major surge over the last two seasons.

Entering the 2023 campaign ranked 15th in the world, Sinner captured four titles, including his first Masters tournament at the Canadian Open, and reached the semifinals at Wimbledon and the ATP Finals title decider.

He signed off the season by beating 24-time Grand Slam champion Novak Djokovic at the Davis Cup and hit the ground running in 2024 by dethroning the Serb at Melbourne Park en route to winning his maiden major.

He added the U.S. Open crown in September and ended the season with a 70-6 match record. His triumphs at Rotterdam, Miami, Halle, Cincinnati, Shanghai and Turin left him with more titles than defeats in a superb campaign.

Incredible season

Sinner's fellow rising superstar, Carlos Alcaraz, won the French Open and Wimbledon titles as the dominant duo shut out Djokovic, the last remaining active member of the 'Big Three,' and put distance between themselves and the chasing pack.

"My goal was to understand what I can achieve this year. There was no specific goal of winning a Grand Slam or being No. 1," said Sinner.

"It's going to be the same next year: whatever we can catch, we take, and the rest we learn. I think that was the mentality we approached this year with, trying to raise my level in specific moments, which I've done throughout.

"I'm happy about that because it's a nice way to finish off an incredible season. A lot of wins, a lot of titles. I believe there's still room for improvement... Let's see what's coming next year. The future, nobody can predict."

Nobody saw what was coming in August.

Anti-doping authorities said Sinner twice failed drug tests in March and had been cleared of wrongdoing by an independent tribunal after it accepted his explanation of unintentional contamination.

With the World Anti-Doping Agency appealing that decision at the Court of Arbitration for Sport, Sinner's spectacular season retains an asterisk for the next few months, with a ban of between one and two years a possibility.

Australian coach Darren Cahill, who joined his team in 2022, said Sinner had been worn down physically and mentally by the doping investigation, but he has been impressed with how the 23-year-old embraced the pressure and finished the season strongly.

"It's not just about winning or losing," Cahill told Italian newspaper Gazzetta dello Sport.

"It's the way you face challenges, and he does it like a champion."