Kane was on Arsenal's books as a child, but the decision was taken to let him go - a choice that has come back to haunt those on the red side of the north London divide.
After a number of loan spells with clubs in the Football League, Kane has flourished into arguably the best striker in the premier league.
He netted his 100th league goal - from his 141st appearance, making him the second-quickest to that landmark - in a 2-2 draw at Liverpool and followed that up with the winner in Saturday's 1-0 success over Arsenal at Wembley.
Those achievements have made a mockery of the Gunners' decision to ditch a very young Kane, and Brady conceded it has come back to bite them.
"He was chubby, not very athletic and we were wrong," he told Corriere della Sera.
"But even Tottenham loaned him three or four times to teams in the lower divisions. But with his determination, he is building a great career. And he deserves it.
"That boy has a character that drives him to always improve.
"After [Lionel] Messi, [Cristiano] Ronaldo and [Robert] Lewandowski there is him. The numbers say it. And he's only 24 years old."