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

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).

Learner Tien won again at the Australian Open today, knocking out France’s Corentin Moutet to progress to the fourth round of the men’s singles.