Australian Open: Daniil Medvedev stunned by 19-year-old Learner Tien

In the upset of the tournament, the 19-year-old recovered from losing a two-set lead to beat the fifth seed 6-3, 7-6(4), 6-7(8), 1-6, 7-6(7) to reach the third round of a Grand Slam for the first time.

Tien initially held a match point in the third-set tiebreak to seal what would have been a straight-sets win, only for Medvedev to save it on serve - and then force a fourth set.

The Russian ran away with the fourth set and it looked like he had finally broken Tien's resistance in the 11th game of the decider, breaking to serve for the match.

However, Tien broke straight back - and won the deciding 10-point tiebreak close to 3am local time.

"I mean, I was definitely hoping it wasn't going to go to a fifth-set breaker," joked Tien in his post-match interview. "Either way, 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.

"Losing the third [set] was tough after playing for that long â- I had a match point. I didn't really get touch the ball I don't think, I think it was an ace.

"That was a little disappointing, to see a fourth [set] after fighting from a break down in the third. Honestly, in the fourth set, I just had to pee so bad â- so I was just trying to finish it up fairly quick!

"I also wanted to start the fifth set serving, so I dropped out that game at 0-5 and it all worked out."

Tien started the Australian Open qualifying event as the world No 121, seven spots off his career-high of world No 114.

However, having won three qualifying matches and then beating Camilo Ugo Caraballi in round one, the US star is now set to crack the top 100 following this win over the former US Open winner.

The 19-year-old is provisionally up to 96th on the ATP Live Rankings, holding 607 points as things stand.

He is the third teenager to beat a top-10 player this tournament, with 18-year-old Joao Fonseca beating world No 9 Andrey Rublev, and 19-year-old Jakub Mensik having defeated world No 6 Casper Ruud.

Those wins, coupled with 20-year-old Alex Michelsen's win over 11th seed Stefanos Tsitsipas, could represent a significant incoming shift across the ATP Tour over the next 12 months.

Medvedev's loss also ensures that there will be an unseeded quarter-finalist in the men's singles draw.

Qualifier Tien next faces Corentin Moutet, with the winner of that then taking on Lorenzo Sonego or Fabian Marozsan in the round of 16.

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