I don't buy this "lost the dressing room" stuff that gets trotted out about managers.
If players have basically stopped trying because they don't like the person they are working for, then that's a problem in the character of the players rather than the manager.
Newcastle's problem is that they overachieved last year. On the back of that, Pardew has then gone out and spent money on some pretty mediocre players from what is - PSG apart - a pretty mediocre league. Not only do they appear to be technically and tactically suspect, but psychologically too. Debuchy's obvious attempts to get himself sent off at the weekend are a prime example.
Where Newcastle are in the league right now is probably 4-5 places below where you would expect that group of players to be, but that's all IMO. They're not a top six side by any stretch of the imagination, they probably don't have a single player that a top six club would want if they put them all on the list tomorrow.