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

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 friends from California, Learner Tien and Alex Michelsen, have both reached the fourth round at the Australian Open. Tien is 19, and Michelsen is 20.

American teenager Learner Tien produced arguably the biggest shock of the Australian Open so far as he defeated last year’s runner-up Daniil Medvedev in five sets, 6-3, 7-6 (4), 6-7 (8), 1-6, 7-6 (7).

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

The Irvine native and 19-year-old qualifier, who played one semester at USC, wins a 4-hour, 49-minute thriller that ends at nearly 3 a.m. in Melbourne

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