Di Canio launched an angry attack on the discipline of his squad after Phil Bardsley was pictured laying on the floor of a casino covered in £50 notes.
Bardsley was left out of Sunderland's squad after the picture of him - taken after the club's survival was assured on Tuesday night following Wigan's loss at Arsenal - was printed in The People newspaper on Sunday morning.
Di Canio claims the mentality he has encountered at Sunderland is worse than that of League One side Swindon, who he managed before taking charge at the Stadium of Light.
Bardsley accepted being left out of the squad, and denied that he was drunk at the time.
"I saw the picture on a website and moments later he was out of my squad," Di Canio told a press conference.
"How can I play a player that probably is blurry for three, four days after what's happened?
"I want to deliver a very clear message: there is no excuse to behave like he did.
"They went out because Wigan lost the game and we stay up.
"I could understand it if we had won the Champions League or maybe the FA Cup.
"We have to respect the dignity of the club, and the fans.
"I thought that at Swindon... arrogant, ignorant footballers because they've not had many chances to stay at the top level.
"I have to tell you unfortunately I found a worse environment in terms of discipline in this club.
"This is what I've found in the last few weeks so we have to change completely."