American teenager Learner Tien stuns No. 5 Daniil Medvedev in Australian Open

There's been a stunner at the Australian Open, and it came from an American teenager.

Qualifier and 19-year-old Learner Tien beat No. 5-ranked and three-time Australian Open finalist Daniil Medvedev in a five-set thriller 6-3, 7-6 (4), 6-7 (8), 1-6, 7-6 (7) for the biggest win of his young career.

After capturing a two-set lead, Tien appeared to be slipping when Medvedev mounted a rally to tie it and take it to the decisive fifth set. However the teen stayed composed and secured match point off a return from Medvedev that went out of bounds, capping off the major victory in a nearly-five hour match as the clock nearly hit 3 a.m. in Melbourne.

"I’m just really happy to get a win. I know I made it a lot harder than maybe it could have been, but whatever," Tien said in his on-court interview after the victory.

With the win, Tien became the second-youngest American man to reach the third round at the Australian Open after Pete Sampras did it in 1990 at 18 years old.

What to know about Learner Tien

A native of Irvine, California, Tien was a successful juniors player before he become a professional.

He won the 2022 and 2023 USTA Boys' 18s National Championships, which got him wild-card entries into the 2022 and 2023 US Open at the ages of 16 and 17, respectively. He made it to the junior finals of 2023 Australian Open and US Open and played a semester of college tennis at Southern California for the 2022-23 season before opting to turn pro. From May to July, he went on a 28-match winning streak.

Heading into the tournament, Tien was 0-3 in Grand Slam appearances and is currently ranked 121st. He beat Camilo Ugo Carabelli in the opening round of the tournament before pulling off the upset against Medvedev. Now Tien will face Corentin Moutet in the third round.

This article originally appeared on USA TODAY: Learner Tien stuns Daniil Medvedev at Australian Open