Sunderland manager Paulo Di Canio is a "strange person" who has a lot to learn about the job, the club's defender Titus Bramble was quoted as saying by British media on Wednesday.
Bramble, who will leave Sunderland at the end of the month, said the Italian coach was making big mistakes and was in danger of losing the support of his players.
"I've never played under anyone like him and I've played for some of the best managers around," Bramble said in the Daily Telegraph.
"He thinks he knows everything but he has got a lot to learn.
"He's a young manager trying to stamp his mark on things but he's making some big mistakes... He was fine at first but he's a strange person."
Di Canio arrived at the club in February amid controversy surrounding his political beliefs and later denied he supported the "ideology of fascism".
He managed to keep the club in the Premier League but, according to Bramble, his abrasive man-management style has ruffled feathers within the camp.
"He comes out in the media and hammers players and he hasn't said a word to them. Imagine how Connor Wickham felt when he was told by his family what the manager had said about him (being too worried about how he looks) in the press.
"He's never said anything like that to his face. He's 19 and the manager is battering him in the media...
"He seems to be more worried about his image outside of the club, sounding good in the media, than anything else. It's a dangerous game to play."