Jannik Sinner had 'no idea' who Carlos Alcaraz was as locker room encounter revealed

and have reflected on their first ever meeting at an ATP Challenger Tour event when they were teenagers.

The young stars have gone on to become two of the best players in the world, splitting the four Grand Slam titles in 2024. But their rivalry started in the first round of the Alicante Challenger five years ago.

Sinner has now admitted he had "no idea" who the Spaniard was but he was keen to get to know him after being beaten by him and met his young rival in the locker room.

Sinner and Alcaraz have formed one of the most exciting rivalries in tennis. They've already met 10 times with the world No. 3 leading their head-to-head by six wins to four losses.

Both have reached the top of the rankings and won multiple Grand Slam titles - Alcaraz has four and Sinner clinched his first two this year. They've faced off at Majors, Masters tournaments and in finals.

But their rivalry started on a modest clay court in Villena, where they were drawn to face each other in the first round of the Alicante Challenger in April 2019. Both had received wildcards into the main draw.

Alcaraz was just 15 years old and Sinner was 17. Playing on outdoor clay at the Juan Carlos Ferrero academy, the Spaniard needed an hour and 50 minutes to seal a 6-2 3-6 6-3 victory.

It was the first of many meetings. More than five years later, as they both competed at the season-ending championships in Turin, the rivals sat down to share their first impressions of each other.

"I saw the draw coming out and saw Carlos Alcaraz, I had no idea who he is," Sinner told CNN. "I saw his age and said wow, he's playing a Challenger, it's amazing. Straight away, I was impressed."

Although the world No. 1 had never heard of his opponent, he quickly learned that Alcaraz was one to watch after losing to the then-unranked Spaniard and wanted to share a locker room with him.

He continued: "After the match we went to the same locker room because I wanted to get to know him. He was an amazing talent already back in the day, you could see straight away he was a special player."

It was a nervy match - Alcaraz lost serve five times and Sinner was broken seven times. And the 21-year-old remembers the ebbs and flows.

"The match was a rollercoaster but it was great," he recalled. "I didn't think at the time that we were going to share a lot of tournaments or become the players we are now because it was impossible [to think so far ahead]."

Now only 23 and 21 years of age, Sinner and Alcaraz have already enjoyed Hall of Fame-worthy careers. When they met in Alicante, they never would have expected to reach the top of the game together.

Alcaraz added: "When you are this young, you don't even think that far [ahead]. All dreams."