Keane believes Tottenham's second half collapse was telling.
He told ITV: "Inexperience was huge tonight, Juventus found a way to win and Tottenham found a way to lose.
"Instead of killing the game off, Tottenham should have played like Juve when they went in front. Three or four minutes of madness has cost them.
"It's hard to understand how Tottenham lost the game. What Juventus did was stay in the game.
"They had a bit of luck with Kane's header (cleared off the line) but these players have won title after title."