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 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 has stunned the tennis world, claiming an upset victory over Daniil Medvedev at the Australian Open.