He ran a 44.13 world lead in 2010, He was injured 2011, and he has clocked at 20.53 for 200m in bad conditions in his pre-competition period.
This is where you guys show how little you know about track. If he is running 20.53 pre-comp he is likely in 20.2 shape or faster at the moment for 200m. His 200m Pb is 20.19 so his speed is no differant now to what is has been his entire career. He is 28 FFS.
He ran low 20's as a teenager so he wasn't juicing to get the speed he needed. Something has changed and that is NOT his speed, its his endurance.
400m equation at the best circumstance is typically best 200m x 2 + 3 seconds. Therefore 20.2 x 2 + 3 = 43.4. At the moment his endurance appears to be 200m x 2 + 4.5seconds.
Btw: If you Jeremy Wariner and your endurance is not going too well the 800m seems like the perfect event to move up do... Sarcasm Alert