Why, many teams do it and don't look back.
Everybody should be willing to take that route after seeing how horrible a 7 year vet 3 year starter played.
IMO, there are 3 basic factors to a rookie coming in and starting.
1 - he is better than Tyrod
2 - he is worse than Tyrod
3 - he is equal to Tyrod
To me there is a 67% chance that we get equal to or better QB play with a rookie. I like the %.