He told the Daily Mail: "You have to defend yourself.
"You take a lot of things on the chin but there are occasions to come out swinging. You can't just sit there and be a punchbag all the time.
"You are under the spotlight at Man U like no other club. It's pages of newspaper coverage, every TV and radio station. To be fair to the manager, he has not thrown in the towel.
'The players have to deal with things. Casemiro was badly exposed playing out of position the other night. From what he produced last season, the wheels have fallen off.
"You hope the younger players have people around them who aren't going to blow smoke up their a*** but tell you how it is.
"Jim Ratcliffe's first priority is recruitment. I've read United have signed 18 players for 50million or more. It is a colossal amount and they haven't got value for money.
'Newcastle have spent, but done it well. Anthony Gordon cost little more than half of Antony.
'Fergie's biggest strength was buying players who served the club for years: Peter Schmeichel, myself, Denis Irwin, Gary Pallister, Roy Keane. Recruitment is key. You want longevity.
"As for the manager, he has to find out why his players aren't fit. They've had something like 14 different pairings at the back. It's unheard of. Centre-backs always getting injured, what is that all about?
"United haven't coped without Lisandro Martinez and Luke Shaw. Raphael Varane has been a great centre-half. Been, not is. He's not available enough."