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

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,

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