The Nerazzurri were thrashed 5-0 by PSG in Munich on Saturday.
Cassano said on Viva el Futebol: "It could have been a joy, instead Inter was destroyed in all respects. Personality, game quality, ideas. It may be fine once, twice or three, but an abysmal difference has been seen. And it must be considered that they didn't have the biggest team in their history.
"The coach instilled the idea of playing the game man to man, (Ousmane) Dembelé I think went 70 times to press on the goalkeeper, taking away the opportunity from the Nerazzurri to start from behind. The worst defeat in a Champions League final."
On the tactics of Simone Inzaghi, Cassano continued: "Inter are very 'capable'. He has no players one on one. Just see on the other side what (Desire )Doué, (Bradley) Barcola did when he entered, Kvara and Dembelé. Inter play this game, for someone they play well, for someone else badly, but it is very predictable."
An exhibition
He also said, "Doué devastated them, Kvara also hurt the full back. It was an exhibition. It went well against Bayern and Barcelona, but 3-4 steps are missing to win the Champions League. In one way or another you can get to the final as done by (Max) Allegri's Juventus, but then you lack personality, quality, a thousand other things that lead you to remedy blows.
"It will be hard to get up, to understand who to start from, it will be very hard, it remains in your mind how I have been carrying 4-0 from Spain for so long."
About Inzaghi, he added: "It is useless to seek faults, it is like shooting on the red cross on this game for Inter and Inzaghi. What could change? Even wanting to change: if you have never changed in 4 years, it is not that you wake up in the morning and try new things. The problem is that the first 4 changes of Inter were 3 defenders and Zalewski. Try to change something, to guide..."