typically 20-1 is ridiculous odds for a starting RB.....however consider that Pittman has few if any TD's this year (maybe 2), and once the Bucs get inside the 6, it's pretty much Alstott as the RB and some other guys comes in as the FB. The only realy chance that Pittman has is to score from about the 15-20 yard line.
If I were to play a Buc (and I probably will) it's going to be Alstott at 7-1. Reason being that the Raider D is pretty good, TB doesn't have the ability to score from long distance so I see a methodical drive with them scoring from a 1st and goal situation...in which case Alstott is in the game.