Barton reckons Ferguson was so bad he didn't know where to put the training cones.
"I am not here to disrespect Fergie," Barton said at the Leaders in Football conference at Stamford Bridge. "He is a great manager, the icon, the pinnacle of British management.
"But he couldn't put on a coaching session to save his life. I've spoken to people about him and he can barely lay out cones. This is not a coach, this is a manager.
"This is the difference - there is a big, big difference between a coach and a manager."
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