Alex Michelsen, a 20-year-old unseeded American, produced the biggest win of his young career with a 7-5, 6-3, 2-6, 6-4 first-round upset of 2023 Australian Open runner-up Stefanos Tsitsipas on Monday.

MELBOURNE, Australia (AP) — Alex Michelson joked that he was too busy at the Australian Open on Saturday morning to have a lengthy phone conversation with his mother back home in California. His excuse was pretty good, actually: The 20-year-old Michelsen was on court for a 6-3, 7-6 (5), 6-2 victory over No. 19 seed Karen Khachanov.

Stefanos Tsitsipas twice smashed his racket onto his bag as he exited the Australian Open in the first round against young American Alex Michelsen. Tsitsipas, who is enduring a miserable run of Grand Slam form,

Alex Michelsen, part of a group of Americans making an impact at the Australian Open, defeated No. 19 seed Karen Khachanov to reach the round of 16.

Alex Michelsen produced the biggest win so far of his fledgling career to upset 2023 runner-up Stefanos Tsitsipas in the first round of the Australian Open and the first person he credited was his mom.

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