That is some pretty high praise, which Alcaraz returned in kind.
"I have never played against him. But I practised in Barcelona with him. But everybody knows his level," said the top seed. "He's a really dangerous player. He has great shots.
"It's going to be really difficult, really difficult match."
Shapovalov showed that danger in a 6-2, 3-6, 6-3, 6-3 dismissal of Arnaldi, a step in the right direction after a clay season disrupted by a left knee issue.
The 24-year-old could only compete in Barcelona and Madrid on the road to Roland-Garros, posting a 1-2 match record. He might be underprepared, but the Canadian is relishing the chance to show what he can do when up against the best.
"It's going to be a challenge. It's going to be a tough battle. He's a great player, obviously everywhere, but especially on clay courts. Three out of five is not going to be easy against him, but I'm looking forward to it," he said, looking ahead to a first third-round appearance here in Paris.
"Honestly, going into this tournament I didn't really know what to expect. I was barely playing any tennis, just trying to see how the knee is this week and try to play as much as possible."