The interesting thing about this is how much it speaks to Martinez's alleged stubborness. He has a philosophy and is reluctant to stray from those ideals year-to-year.
Stubbornness? it's because you can't as a manager, it costs too much.
Nowadays, you have your formation, kids in the Academy will play it at all age groups so it's engrained. The transfer policy/scouting looks for players that fit into that formation, and it would require the re-education of the 70-80% of players that could make the switch.
When a new manager comes in and changes the philosophy of a club there is usually a huge turnover of players and a downturn in performance while everyone gets used to it. Look at the problems ManUre are having trying to switch to a back five. Hell, even going more direct shows up a lack of ability in long range passing and requires the replacement of tippy-tappy footballers who are comfortable in possession. Players are chosen to play in a style or formation, change that and you have to look at other players.