Our ability to identify offensive line talent is pretty poor. The strange thing is that both Snyder and Colledge graded out very, very poorly prior to us signing them to large contracts. Each of them were seen as the weakest link on the line of their prior teams. Snyder specifically graded out as the worst guard in the NFL last year I believe. PFF also recently named him the least valuable guard per investment in the NFL.
They said the following:
"It’s gotten to the point where I almost have to apologize when writing about Synder. I mean it feels like I’m repeating myself but what else am I meant to do? It may not seem a lot to invest $2m in a right guard, and it’s not. But when your right guard is so bad he hurts the team with his ability to guide pressure to the quarterback it needs mentioning. Can’t blame Snyder here, the tape was there to show what kind of player he was. Inexcusable decision in signing him."
https://www.profootballfocus.com/blog/2012/11/01/cap-hit-bad-value-for-money/
It's incredibly frustrating.
For what it's worth, PFF has Colledge rated as the 12th best pass blocking guard out of the 51 who qualify.