I have a feeling that he is not really looking to kill himself to win this one. that would be my approach anyway given his issues with the knee and overall health.
its not worth giving up 2014 in case the knee goes again.
what he is doing is racking up points and that appearance fee which is probably around $2 million now. so he is raking in the cash and the points in order to try to lock up the #1 rank.
that would be my guess anyway. he will take any and all matches that come somewhat easily but make sure that he does not have to go so damn hard that it leads to injury.
at any rate, he should get on clay after shanghai masters to practice and skip paris and basel.