Four and a half years ago, Rafael Nadal was already predicting great things for Denis Shapovalov after being given a crystal-clear warning of the massive threat posed by the Canadian tennis prodigy.
The setting was the round of 16 at the 2017 Montreal Masters and Nadal was aiming to wrest the No.1 world ranking back from Andy Murray, then at the peak of his powers.
But his bid was derailed by Shapovalov -- then aged 18 -- who made the most of his wildcard to pull off a memorable 3-6 6-4 7-6 (7-4) victory on home soil.
Nadal has won the subsequent three meetings between the pair, including another epic on the Spaniard's beloved clay at last year's Rome Masters that also went to a final-set tiebreak.
But, somewhat surprisingly, Tuesday's quarter-final clash at Melbourne Park will mark the time the pair have clashed at grand slam level.
"That was a a tough one, that one, I remember because I was playing for the No. 1," Nadal recalled of his first encounter with Shapovalov.
"He played great.
"Honestly, he was very young and he played with amazing intensity and created amazing shots.
"As everybody knows, is one of the players with the biggest potential on the tour.
"When I played against him, after the match I said he's going to be a potential multi-grand slam winner.
"And I still think that if he's able to keep improving, he will be a multi-grand slam winner.
"He has a lot of amazing things on his game, and his results says that."
The 14th-seeded Shapovalov has not quite delivered on that promise just yet, but his career is trending in the right direction, as evidenced by a run to the Wimbledon semi-finals last year where he lost in three tight sets to Novak Djokovic.
Shapovalov had a rough start to his southern hemisphere summer campaign, testing positive to COVID-19 on arrival in Australia in late December.
But he recovered in time to help Canada claim the ATP Cup in Sydney and has improved with every match at Melbourne Park, culminating in a straight-sets victory over world No.3 Alexander Zverev in the fourth round on Sunday.
"I'm definitely expecting a long battle out there (against Nadal)," Shapovalov said.
"Obviously he makes you play a lot.
"His defence is very good and he's very good at what he does.
"So I'm going to have to try to play my game, take it to him and keep doing what I have been doing; playing patient, fighting for every point, and just picking my spots to play aggressively."
Shapovalov and fellow young gun Felix Auger-Aliassime have joined Milos Raonic (five times) and Mike Belkin (1968) as the only Canadian men to have made it as far as the last eight at an Australian Open.
Auger-Aliassime outlasted 2014 US Open champ Marin Cilic 2-6 7-6 (9-7) 6-2 7-6 (7-4) in the fourth round on Monday.
