Player movements is Marwoods role pretty much from top to bottom Once tragets or player surpless is identified its his job to bring them in or farm them out.
It is a commitee with Mancini and his staff heavily involved. They factor is alsorts
eg Gareth Barry
Should we sell him this summer?
No: First team choice, very consistant, good engine, good pro, not the highest earner
Yes: 31 now so might not play 3 games a week, value is depreciating as his contract and age move on so re-sale value is at peak now, what other players are available
There is almost endless data goes into these decision, City have a decision science team that create models and bang in data from sources all over the club from finance, to scouts, to coaches and produce analysis.