If Colon comes back this week but Adams does not, I'd say DeCastro starts at his natural position and Foster moves over to RT where he was surprisingly effective a few months ago.
If Adams comes back this week but Colon does not, then DeCastro could play out of his comfort zone at LG, but he should still be better than Legursky, who seems to be a disaster anywhere but at center and goalline fullback.
If neither Colon nor Adams comes back this week, I'd probably rather use Beachum inside rather than outside. Insert Beachum at Colon's spot (although #68 lining up at LG again gives me the heebie jeebies), then have DeCastro at RG and Foster at RT.
I was the biggest DeCastro supporter in the world leading up to the draft, so I'm excited to see what the kid can do, especially now that we really need him with all of the OL injuries. If he does indeed play at his usual RG spot, there is no better "throw him into the fire" test by having him face off against Haloti Ngata right off the bat.
Final Ruthless Mock:
1.22 CB Marcus Peters, 6'0" 197 lbs., Washington
2.56 FS Damarious Randall, 5'11" 196 lbs., Arizona State
3.87 TE Clive Walford, 6'4" 251 lbs., Miami
4.121 DE Henry Anderson, 6'6" 294 lbs., Stanford
5.160 WR Titus Davis, 6'1" 196 lbs., Central Michigan
6.199 OLB Kyle Emanuel, 6'3" 255 lbs., North Dakota State
6.212c OLB Max Valles, 6'5" 251 lbs., Virginia
7.239 RB John Crockett, 6'0" 217 lbs., North Dakota State