Point tracking is no good in this situation. You’ll have to hand track the best you can, estimating the forward-most position of the blur-producing object. When the footage speeds up you can ramp up the motion blur on your attached layer, maybe with CC Force Motion Blur.
I think the only other option worth your while would be planar tracking.
If the shot is critical you could download a trial of Mocha AE and give that a go. It usually works miraculously well, even on otherwise ridiculously problematic tracks, though I’ve never tried it with blurred subjects.