San Francisco Frontiers - Teen qualifier Tien surges into Australian Open last 16

The American 19-year-old won 7-6 (12/10), 6-3, 6-3 in Melbourne with Moutet collapsing clutching his leg in the third set before gingerly carrying on.

The victory extended Tien's remarkable tournament after he stunned last year's runner-up and fifth seed Daniil Medvedev in a five-set thriller in round two.

No other American man his age has gone so far in Melbourne since Pete Sampras in 1990, with Tien's reward a clash against Italian Lorenzo Sonego or Hungary's Fabian Marozsan.

"It feels great, obviously," said Tien.

"This has exceeded my expectations, what I was hoping for coming into this week.

"You go into every match believing you can win, but to be in the second week is amazing."

Tien is one of a trio of teens who set the Australian Open alight with wins over top-10 players, alongside Brazil's Joao Fonseca and Jakub Mensik, who have both been knocked out since.

In a battle of left-handers, Tien broke early for a 3-1 lead in the first set on the back of an unforced baseline error from Moutet. But the Frenchman levelled at 3-3.

Another exchange of breaks sent it to a dramatic tiebreak that ebbed and flowed before Tien clinched it 12/10, ending a 72-minute set.

The American broke twice in set two to seize control of the match before Moutet collapsed to the ground clutching his left leg after serving at 15-0 in the opening game of the third set.

He got back up and gamely attempted to continue, but was clearly in pain with his movement restricted and Tien took advantage to book a place in a maiden Grand Slam last 16.

"All the best to him. Wishing him a speedy recovery," said Tien. "I didn't really see what was going on ... I just saw him on the ground.

"I didn't want the match to end like that. But he told me he was going to keep trying just for me."

L.Ramos--SFF