RB Start opinion

Who would you start in a 12 team standard league?
Pick 2 with the best upside

I own these guys
RoJo @ NO
Singletary @ MIA
Mattison @ DEN
Murray @ TB

These guys are on waiver wire
Mostert @ ARI
Pollard @ DET
Darrel Williams @LAC

I think Singletary and Mostert have the highest upside