Released Sunderland defender Titus Bramble has taken a swipe at the management of Paolo di Canio.
Striker Connor Wickham was also compared to a "playboy model" by Di Canio.
Bramble, whose contract with the Black Cats expires this month, told the Daily Telegraph: "I've never played under anyone like him and I've played for some of the best managers around. Steve Bruce, Roberto Martinez and Sir Bobby Robson. He thinks he knows everything, but he has got a lot to learn.
"He's got a long, long way to go before he gets anywhere near as good as Sir Bobby Robson. He's a young manager trying to stamp his mark on things, but he's making some big mistakes.
"He's targeted the easy players, the ones who are leaving anyway, trying to show he's the boss. I was fined for not going to a weights session. Everyone else at the club thought it was ridiculous, but he's trying to be tough.
"He comes out in the media and hammers players and he hasn't said a word to them.
"He's never said anything like that to his (Wickham's) face. He's 19 and the manager is battering him in the media."