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

Learner Tien, a 19-year-old from California, became the youngest American man to reach the Australian Open's third round ...

Learner Tien upset a fifth-seeded, racket-tossing Daniil Medvedev in the second round of the Australian Open, a five-setter that took nearly five hours.

Australian Open marks the first Grand Slam of the tennis season. Much has changed since the most recent Slam, the U.S. Open ...