Start Hill or Walker?

Should I start Tyreek Hill @ Tennessee or Kenneth Walker @ Detroit?

Hill has been a mess without Tua with 1 catch last week, Walker has been on a roll. Tua is "expected to be back week 8 but still has not practiced and no reports here in Miami.

IF he does I would be leary for game #1. but will add if he clears concussion to play and after practice.