Di Canio was reacting to a week which saw Juventus thrashed by Galatasaray and Inter Milan humiliated by Bodo/Glimt in their Champions League playoff ties.
The West Ham legend said on Sky Italia: "Let's leave aside the Premier League, which is a completely different league. The same goes for other European teams: Qarabag even beat Barcelona once, but that doesn't mean the Azerbaijani league is the strongest in the world.
"The Italian perception of us is that we're phenomenal, and then we concede six goals to PSV. This year, they thought Napoli could get who knows where in the Champions League and then they conceded six goals from a team that took three points against Napoli and then five points in their other seven games.
"Inter conceded five goals in the final against PSG, but they could have conceded ten goals."
Then examining Donyell Malen's instant impact with Roma after joining from Aston Villa in January, Di Canio continued: "He's 27 years old and no one's ever paid attention to him. Yet we commented on him in the cup games with Dortmund, where he was little more than a reserve, a co-starter, okay?
"At Aston Villa he was rightly a reserve for (Morgan) Rodgers and especially (Ollie) Watkins, who are stronger. He arrives here, scores five goals in five games and who are we going to mention? (Gianluca) Vialli? My big brother, a kiss to the sky, I'm sorry they mentioned you."
He then turned on Juventus coach Luciano Spalletti, adding: "He says '(Liam) Kelly doesn't even know how good he is!', but in reality he's a fool. In a good way, of course, because he's a great guy, but there's no narrative, even from coaches, that leads people to believe Kelly can become a Juventus centre-back who maybe wins the league and the Champions League.
"Sure, they say that every now and then to motivate the players, but then they put in performances like what happened with (Andrea) Cambiaso."