For Murray to become #2 after IW:
Win IW. Doesn't matter what Federer does.
Reach the final; Federer goes out in QFs or before.
Even if he doesn't catch him, he has a huge chance to significantly close the gap here. Really needs a good tournament, no more first game defeat crap.
However it is worth nothing that whatever happens, it might be short-lived with Murray defending 600 from Miami (Federer will lose 90). Although he will be 2nd seed.
Thanks a lot for that info, TMH.