WOW, holy crap. This is a tough call.
Johnson - coming from a Viking fan, I think is going to be an issue for us. Just look at what B. Marshall did in his two games against us. (12rec w/ 92 yd & 10rec w/ 160 yds w/ 1TD) We have a tough time containing great #1 WR's and thats what Andre is. Plus he is a beast at home, 8+ receptions in his last 3 home games all with 118 yds or more.
Dez - gotta start him. This game should be a shoot out with NO and he has 6 consecutive games with a TD with 8 TDs total over that span.
This leaves Cobb and Thomas but I think I would go with Cobb here. Denver still has Decker plus a good ground game that could steal looks away from Thomas where as GB has really focused their offense around Cobb and they have no ground game to be worried about.
This is a tough one but either way you can't look back at your final decision, these are all must start WR's.