Sunderland boss Roy Keane has had a pop at Wigan counterpart Chris Hutchings over their pursuit of Leighton Baines.
Keane said: "I think one or two clubs have tried to use Sunderland. I used to ask myself 'How can managers fall out with each other?' It's easy for players to fall out with each other because you kick each other, but managers?
"Now I'm getting my head round it and seeing how managers do fall out with each other. There were one or two in the Championship but the Premiership is even more lethal. There's a hell of a lot more at stake.
"I'm sure I've made mistakes as a young manager but people shouldn't think that they can walk over us. Managers have rung me up about players and when I say 'Not at the moment' it doesn't go any further with me.
"Sometimes I wouldn't even discuss it with the player but I certainly wouldn't be discussing it with the media. Some managers can't get it out quick enough.
"Maybe that's gone on for a number of years but you do learn about different managers. Some managers have been brilliant, some you think you wouldn't trust him as far as you could throw him.
"I'm not saying that about Chris but he was coming straight out on Sky and saying 'We've had this and that, and we've had a phone call' and he's been going into other people's business. It doesn't have to be said. I was disappointed he made those comments but one or two other managers have done that."
