Demps, an Olympic track star, decided to pursue his track career rather than play football full-time. Rapoport indicates the Bucs were willing to be flexible with Demps' schedule to retain his rights.
Demps is a longshot ever to make an NFL impact. Blount might have an uphill battle just to make the Patriots' roster. Stevan Ridley and Shane Vereen are roster locks ahead of Blount. Leon Washington has a good chance to make the team as a return man. That leaves Blount hoping to be the No. 4 running back. Second-year pro Branden Bolden has a similar power game, but he's more likely to help in special teams.
In short, this is a trade that includes two interesting names but really shouldn't make much of an impact.