But managers do exactly that. It's well documented. In fact, in our 2011/12 season, when the players and Mancini went out to collect the trophy, Mancini blatantly ignored one of the staff and refused to shake his hand. That staff member was Dr Phil Batty, and Mancini hated him as he wouldn't allow him to put players back in the team until he (Dr Batty) felt they were ready.
We had an excellent injury record that season and Batty was largely responsible for that by not rushing players back too early. Mancini had Batty sacked for standing up to him and I think he got the current guy, Dr Sala in.