I will take the minority view and go against Sam. The thing that I think holds Sam back more than injuries is that he struggles to make good throws under pressure. Even when healthy, he appears to have a very low completion percentage when he gets pressure up the middle. Almost all quarterbacks efficiency suffers some in this situation, but from my observations, Sam is similar to Andy Dalton in these situations. The following discussion of Dalton fits my observations for Sam the last two years...
"Dalton must improve his performance under pass rush pressure. His statistics under pressure are miserable: 39 attempts, 101 completions, 38.6% completion percentage, 3 touchdowns, 5 interceptions, 47.3 QB rating. His QB rating drops 46.1 points when you compare unpressured and pressured dropbacks."
Unfortunately I don't have access to this level of stats for college qb's, but that has always been my observation for Sam.