There are so many different types and causes of back pain that it is foolish to speculate what's wrong with Tiger's and what would help it. I've got a weird condition in my back (diagnosed about 2 years ago) where the L-5 didn't form correctly in the womb. Basically, the interior never calcified, so my L-5 has a crispy crust with a gooey center. Sometimes I go months without any pain; other times I play 3 holes and am curled up in the fetal position on the 4th tee box and can't get out of bed for 2-3 days. Aside from stretching, I've never found any correlation between the amount of golf I play and the frequency of the pain.
Tiger might have a similar problem where it's fine and then WHAM! If that's the case, rest and therapy might not matter at all.
If I'm Tiger (meaning if he has something like the condition I do), I go to Bay Hill. If at any point the back starts acting up, or I feel like I haven't had a good warm-up, I WD. Same thing at the Masters, or any other tournament this year.