Pizza celebration for Tien after teenager knocks out Medvedev

Melbourne: Learner Tien celebrated his shock Australian Open victory over three-times runner-up Daniil Medvedev in true teenage fashion, seeking out a well-earned pizza after edging a five-set thriller to progress to the third round.

The 19-year-old American qualifier, making his debut at the year's opening Grand Slam, worked up a huge appetite during an almost five hour-long tussles with the Russian on Thursday, before pulling off a major upset against the number five seed.

"Plain pepperoni," Tien said of his post-match dining plans following a 6-3 7-6(4) 6-7(8) 1-6 7-6(7) win. "Not too many pepperonis. More just cheese."

There was little plain or unremarkable about Tien's victory over his vastly experienced opponent, the left-hander racing clear of the former US Open champion to force Medvedev to fight back from match-point down late in the third set.

The former world No. 1 hauled himself level to take the match into a decisive final set, where Tien prevailed in a tie-break to become the youngest American man to reach the third round since an 18-year-old Pete Sampras in 1990.

"I didn't know that about the age thing actually," said Tien. "That's nice to know.

"I think coming into my match today, I was just trying to treat it like any other match I ever played. Not putting too much importance on just this match today, feeling like this is the biggest match of my life or anything like that.

"I think just taking the positives from this match and looking forward to the next one and moving on."

Tien's progress to the third round, where he will play France's Corentin Moutet, comes as a new wave of teenage talent emerges at Melbourne Park.

Brazil's Joao Fonseca, who defeated Tien in December's Next Gen ATP final in December, knocked out ninth-seed Andrey Rublev on Tuesday while a day later 19-year-old Jakub Mensik defeated number six seed Casper Rudd.

"I think it was definitely pretty inspiring," Tien said of the performances of his contemporaries. "They obviously got those wins before I played my match today. Just trying to almost join them.

"I think just seeing them, the wins they've had this week, just adds a little bit more belief that it's possible."

The victory over Medvedev was Tien's second consecutive five-set success after eliminating Argentina's Camilo Ugo in the opening round, and the youngster's belief in himself is growing, despite being taken into new territory.

"These are my first two five-setters," he said. "I played probably eight, nine hours in my last two matches combined.

"It's definitely a confidence boost to know I can last in these matches, just because I haven't had any five-set experience prior to this week.

"It is nice to feel that I can play these more physical matches and get through them."