Easier said than done.
[speculation] I think that if Moyes has changed completely the training and is making his tactics for percentage football rather than a more modern stykle (and our players aren't made to play percentage football), then they have every right to not play for him (read the next sentence, I am not saying the right to sabotage). In fact, it's not that they won't give it all, simply they won't be able to play that brand which makes us believe that they aren't playing for him. And then will come the shit results and the confidence will be shattered. And if the manager continues doing so, then of course there might be conflicts there and eventually players would want to get rid of him [/speculation]