If Ben was expected to have an impact the 1st year he would have started from day 1. Same with Mendenhall and a few others. In a few RARE cases we had a guy start on day 1... but those cases are few and far between.
Pointing out guys who were forced into starting roles due to injury isn't proof we expected them to have an impact. DeCastro probably wouldn't have beat out Foster if he remained healthy.. he would have probably replaced him later in the season or played due to Gilbert falling on another guy. Again, we didn't draft DeCastro to play on day 1. Fans want us to plug rookies in but the FO uses a different approach.