Canizares believes Vini Jr's form tailed away after his midseason Ballon d'Or disappointment.
He told Radio Marca: "Vinicius can't afford a season like last season, that's obvious. He can't afford it as an individual, nor can Real Madrid.
"Vinicius came into the season thinking about the Ballon d'Or gala, which he had high hopes for, and not winning it has affected him emotionally.
"Real Madrid didn't do well not going to the gala."
On the Brazil attacker's contract talks, Canizares continued: "What I can't understand is that a renewal agreement is reached in April and not signed a week or two later.
"When a player, a club, and an agent reach an agreement for a renewal, everything would be much more peaceful if it were signed immediately."
Prove yourself
He also addressed claims of incompatibility with Kylian Mbappé.
"I don't think we have to sell one; we'll start there," he asserted. However, he warned that "Vinicius can't repeat last year's level, because he'll become a residual player."
And he sent a direct message to the Brazilian: "You may look like a star and have the talent, but to be one, you have to prove it."