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

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

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.

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

Learner Tien, a 19-year-old from California, became the youngest American man to reach the Australian Open's third round since 1990, upsetting No. 5 Daniil Medvedev in five sets.

Two friends from California, Learner Tien and Alex Michelsen, have both reached the fourth round at the Australian Open