It's a definiet upgrade at RB. You are correct that it makes you thin at QB, but I'm all about starting lineups this time of year, so I would make the trade. Have you shopeed him around to make sure Thomas is the best back you can get?
12 Team League. We start 2 QBs and get .5 PPR, otherwise standard scoring
QBs: Stafford, Fitzpatrick, Collins
RBs: Charles, Mendenhall, Best, Starks, Carter, Karim
WRs: D. Jackson, Marshall, S. Smith, Green,
TE: Hernandez, Cook