The Italian was unhappy with the way his side defended at Selhurst Park and admitted that there was a lot of work to do in order to improve his side's fortunes.
One thing Di Canio had no complaints about was the penalty that changed the game. John O'Shea brought down Dwight Gayle inside the penalty with a wayward lunge, earning him a red card.
Gayle converted from the spot to move Palace ahead and Stuart O'Keefe made it 3-1 in stoppage time.
Fletcher had levelled for the visitors but despite large spells of possession, they were unable to claim their first win of the season.
"Today it was difficult to be angry," he said. "Normally I can tell you I'm very angry, but today it was difficult - it was too poor that it was really difficult to say something.
"I don't think that even the most arrogant player in the world could argue if you said the first two goals were absolute rubbish.
"My leader (O'Shea) was already in the dressing room and said sorry to everybody - how can you be angry?
"They are intelligent and understand when they do something bad. I couldn't be angry but obviously I was really sad.
"The second goal was very poor. It came from nothing. My leader let the ball get away behind him and then tried to tackle the opponent and it cost us - the goal and the red card.
"They took advantage from our mistake and they put everything on the field. They never gave up but to be honest their goals were very poor."
Sunderland's only point in the opening three matches came at St Mary's as they drew 1-1 with Southampton.
