There are three American men aged 23 and under in the second week of a Grand Slam. That hasn't happened since 2003

Learner Tien and Alex Michelsen were born about 15 months apart and first crossed paths a decade ago when they were playing in Southern California tennis tournaments for kids. Tien, now 19, and Michelsen,

Learner Tien pulled off a massive upset against Daniil Medvedev at the Australian Open. So, who is Tien, the 19-year-old out of California?

At the age of 19, Learner Tien defeated Daniil Medvedev in a five-set thriller that finished just before 3 a.m. in Melbourne.

By Ian Ransom MELBOURNE (Reuters) -Teenage qualifier Learner Tien became the youngest man to reach the Australian Open fourth round in 20 years as the future of American tennis lit up Melbourne Park on Saturday.

Two of four American men still playing in Melbourne, Irvine native Tien, 19, and Aliso Viejo native Michelsen, 20, became friends on the youth tennis circuit