I'd go for David Nelson. Your set at TE and RB. None of your backups are worst then Knowshon, so there is no point in picking him up. As for David Nelson, he is on what seems to be a very potent offense (I'm buying 100% the Bills offense). It starts with Fitzpatrick and Stevie (who I watched a ton in college and all the bust talks were laughable too me.) Nelson will benefit from Johnson being double teamed. He got 1 less target then Stevie last week. You need WR depth.
I'm buying Nelson 10000x more then Erick Decker as this weeks WW buy. His team is actually good.