The ATP ranking requires players to play in :-

(1) 4 Grand Slam

(2) 8 World Masters 1000

(3) 7 Other Tournaments

(4) ATP Workd Tour Finals

Can a player defy this and not care about the world rankings, theoretically?

I do understand that these tournaments are also needed to transition into playing styles of different courts but I am asking just theoretically what would be the consequences?