Every team projects for a replacement of their QB whether he's great or average. The problem is this is a QB starved league, so most of the time "you luck into" a very good QB as the next step. You hope to draft or acquire good replacements for very good players but it doesn't always work out. Sometimes a team ahead of you in the draft takes your guy. Sometimes...let's say... you have 3 needs on offense but the BPA may be a defensive stud. There are tons of variables and team needs and no organization can fill them all. As for Birks replacement: How do you know that they weren't looking for it, but couldn't find the right guy? Birk's absence was not all that was wrong with the line. Yanda was 60% coming off an injury, Oher just played shitty.. KO got injured and Monroe was new. and Rice forgot how to run and then he got hurt. Joe lost Boldin and Pita and had nowhere to throw the ball. There was a lot more wrong than just Birks absence.