The 19-year-old who was a late qualifier to the Grand Slam secured the biggest win of his young career on Thursday

American teen Learner Tien pulled off the biggest upset so far at the 2025 Australian Open, ousting Russian Daniil Medvedev -- the No. 5 player in the world -- in a 4-hour, 49-minute thriller at Margaret Court Arena.

Learner Tien, 19, became the youngest American man to reach the Australian Open's third round since Pete Sampras in 1990.

Teenage qualifier Learner Tien stunned last year's Australian Open runner-up Daniil Medvedev after Jannik Sinner roared back to take his place in the third round.

Jannik Sinner and Aryna Sabalenka will be the defending champions at the 2025 Australian Open - but who will their biggest rivals be in the singles draws?

Jannik Sinner will try to put a doping scandal behind him when he kicks off his Australian Open defence against Nicolas Jarry, while Aryna Sabalenka's bid for a hat-trick of titles starts on Sunday against Sloane Stephens.

Defending champion Jannik Sinner lost his first set since October but recovered to beat Tristan Schoolkate and reach the third round of the Australian Open.

Daniil Medvedev ripped 24 aces and converted six break points to outlast Kasidit Samrej in a 3-hour, 8-minute first-round victory Tuesday at the 2025 Australian Open. No. 9 Andrey Rublev was the latest upset victim.

Defending champion Jannik Sinner and 10-time Australian Open winner Novak Djokovic have landed in opposite sides of the draw for the season's first major, ruling out a replay of last year's semifinal encounter.

Russia's Daniil Medvedev reacts during a press conference ahead of the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 10, 2025. (AP Photo/Ng Han Guan) Aryna Sabalenka ...