Martina Hingis: it will be extremely difficult coz the bulk of her points come from teh first couple of months with her win in Sydney (Tier 2) final in Aussie, then two Middle east tourneys (tier 2 I think). So Realistically it will be very hard for her at the start of year with possibly drop a couple more space if she is not in form.
Kim Clijsters: Better chance then most, can actually exploit tjis spot if Jenny do not start well. Hardly have any point to defend until US hardcourt season start. If she start off the season with a bang ( a semifinal in Aussie and a couple of final finish in a few smaller scale tourneys) which is likely looking at her form. Jenny or Lindsay may lose this spot to Kim, not much chance for Venus, coz her only major points will be Aussie semifinal which is hardly anything, compare to her second half.
Serena Williams: she is an unknown quantity, got a few points to defend but nothing really major until Indian wells, if she stick to her promise and start playing more, than if she is in form (ie, a win and a few semifinal and final finishes) will propel her a no.3 rank with no problem. But all this have to depend on how well prepare she is for the start of season.
Justine Henin: She is an unlikely candidate to go to no.3 out of this group unfortuneately. She iwll get it one day but definitely the first, because she got a bulk of her point right at the start of the year with her 13 winning streak, although given her high rank, she should go further in Aussie. Again, if she maintain her standard like start of last year, she may well find herself in this spot by clay court season. (having said that it all depends on how well teh other candidate does)
Amelie Mauresmo: Unfortuneately she is more slim in chances coz she got two tourneys to defend right after Aussie and the fact that her majority of her point come before French Open and the fact that she has hardly anything at the second half of teh season do not help her prospect at all.
<br />Having said that, we can never tell, who knows if one of those candidate will pull off a Jenny at the start of year, then everything will be completely different