So Nadal will lose 90 points from Doha and 1200 points from AO, leaving him at 5400.
This means that even if Ferrer loses in the first round at AO, he will become #4(unless Berdych wins AO) once the AO points are dropped(when will this happen? this change of schedule every year is getting on my nerves
Nadal has enough points to stay at #5 unless Berdych reaches the AO final or DelPotro wins AO.
it will happen after the AO. Ferrer will be at worst number 4 (he can be number 3 if he reaches AO final and Murray doesn't reach QF) unless Berdych wins the Australian open and Chennai and Ferrer loses before QF, or Berdych wins the Australian open only and Ferrer loses before R16.