Sanchez could remain a starter if he doesn't lose effectiveness:
http://m.bluejays.mlb.com/news/article/185246490/blue-jays-gm-ross-atkins-discusses-season
MLB.com: What is the latest on Sanchez going to the bullpen?
Atkins: I think often times in the industry, people will follow norms that obviously can be informative, but we have to make sure we individualize it and are working off the information that Aaron and the league and offences that are playing against him are giving us. So, how he's feeling, how he's performing objectively and subjectively; not necessarily the results, but in terms of release point, in terms of velocity and spin rate. As we see those things potentially changing, then we'll start to consider what the best thing is for him. This is an easy one for the most part, because he has a chance to really be a game-changing starter for the rest of his career and we wouldn't want to impact that in a negative way.