Roger Federer will need to avoid a second Grand Slam upset at the hands of home favourite John Millman if he wants to bring up 100 wins at the Australian Open on Friday.
The 38-year-old Swiss, already the first man to win 100 matches at Wimbledon, can match the feat in Melbourne if he beats Millman, ranked 47, in the third round.
But the 20-time Grand Slam champion is well aware of the challenge posed by Millman, after he was shocked by the Australian in four punishing sets at the 2018 US Open.
"I think the next match is really going to be a test for me because John is going to be there. He's fit like a fiddle," Federer said.
"He's from this country, so naturally also it's going to be different intensity. I think this is going to be a good test for me."
Friday's glamour tie is between 15-year-old American Coco Gauff and defending champion Naomi Osaka, 22, the second instalment of a rivalry that could run and run.
Osaka destroyed Gauff at the same stage of the US Open last year but the assertive teenager insisted it will be different this time around.
"She plays really aggressive. This time coming in I'm going to be more aggressive," said Gauff.
"I think I'm more confident this time around."
Serena Williams, seeking to end her quest for a record-equalling 24th major title, plays China's Wang Qiang, while Australia's world number one Ashleigh Barty faces Elena Rybakina.
Reigning men's champion Novak Djokovic, who dismissed Tatsuma Ito in round two, will face a second Japanese opponent when he plays Yoshihito Nishioka.
Defeat is almost unthinkable for the seven-time Melbourne winner, who dropped only three games to Nishioka in their only previous meeting at last year's Davis Cup.
Sixth seed Stefanos Tsitsipas will face a sterner test against Canada's Milos Raonic, a quarter-finalist last year, while Italy's Fabio Fognini, who has already survived two five-setters, plays Guido Pella.
