Alcaraz tips 'incredible' Fonseca to be among world's best 'soon'
The fearless 18-year-old Brazilian qualifier stunned ninth seed Andrey Rublev in straight sets on his Grand Slam debut on Tuesday.
Fonseca last month became the second-youngest champion of the NextGen ATP tournament since current world number one Jannik Sinner claimed the title, also aged 18, five years ago.
Alcaraz, himself only 21, was suitably impressed.
"What can I say about it? Just incredible. I mean, the way he played his first Grand Slam match against his first top-10 player, it's unbelievable," the Spaniard said after easing into the Melbourne third round.
"The way he approached the match, the way he handled everything, the nerves, the match in general, it's been fantastic.
"He's going to be there," he added of the 112th-ranked Fonseca making it big.
"It's just the beginning of the year, just one win in a Grand Slam, but he's going to be there.
"We're going to put Joao Fonseca's name on the list of the best players in the world really soon."
Fonseca backed up his NextGen crown by winning an ATP Challenger Tour title in Canberra this month.
He then powered through qualifying at Melbourne Park and is now on a 14-match win streak with his next opponent Italian Lorenzo Sonego, who is ranked 55.
"For sure, the NextGen gave me confidence. I mean, I'm playing great tennis, so I need to enjoy this moment, to play my best," Fonseca said after beating Russia's Rublev.
"I'm playing good, so I'm feeling confident.
"I think when I arrived here, my first goal was to qualify for the main draw. Of course, my expectations are bigger now," he added.
"I want more and more."