Which player should I drop to add Vincent Jackson?

[joemint]

I would like to take a chance and pickup Vincent Jackson especially now his suspension is down to 4 games. I am in a 12 team PPR league. Below is my team:

QB - Tom Brady
WR - Jennings
WR - Bowe
RB - Gore
RB - Moreno
WR/RB - Hillis
DEF - NO
Bench - Spiller (RB), McGahee (RB), Knox (WR), Breaston (WR)

In my league, most of the players tend to hoard RB so not many good RB are available. So I am reluctant to drop a RB. I am leaning toward dropping Knox or Breaston. Breaston is clearly no. 2 especially now Early Doucet is out 3-6 weeks and it is a plus that Fitz is not 100% healthy. Knox on the other hand is on Martz offense but it not quite clear if he is no. 1 or no. 2 WR. Which one do you think has the most upside? Thanks.