I think overall Clark will end better than Keller. He has a lot of upside with him. However, Keller is still one of the better TEs so it's not much of a downgrade for you. Gaining McFadden should boost your RB production when he's healthy. Even if he does split carries, he should be a decent option at least to work match ups.
10 Team; 1QB/2RB/2WR/1Flex/1K/1D; Standard; Non-ppr
QB: Vick, Orton
RB: Forte, Bradshaw, Addai, Lynch
WR: D.Jackson, S.Smith(Car), Garcon, Bess, Blair White
D: Phi, Ari