Here's my theory based on what we know so far, what has happened in the past and what we know about the personalities involved. Possibly cobblers, maybe a hint of truth.
The players aren't happy with Wiliams. That much seems certain. So Grimes, in his capacity as "Captain", and as we know he has done before, has gone to Coleman to whinge about it.
Coleman, undoubtedly suffering from his own buyers remorse over Williams, facing the headache of finding a replacement during a transfer window that they'd already planned for and well aware that Grimes' griping was one of the reasons why we found ourselves in the position of needing to appoint a new manager in the first place, has lost his temper and basically told Statty to shut up and play, to do what we're handsomely paying him to do and stop pretending that he's the one in charge.
Grimes has gone to the rest of the squad for support and found out that he is perhaps not as universally popular as he might have thought. Lots of them are new, many may be harbouring their own doubts as to whether a style of play that seems to have been custom designed to suit one man may not be ideal to make the best out of their own talents, and would be quite happy to change things up in a way that Grimes would not like and have told him so.
MG's agent suddenly finds himself with extra work to do.