The term "sleeper" can mean a different caliber of player to different people. I've read comments recently that players such as Brett Anderson and Pedro Alvarez are "sleepers" for this season. Considering they are both generally going among the top 150 players taken in mixed leagues, I don't think the term applies in their case, and I want to go a bit deeper than that. A player such as Jordan Zimmermann has generated enough buzz (and is going in the top 200 in some drafts this preseason) that I'm not sure he fits the term, either.
I don't forget about those who play in deep single-league formats. I actually prefer them to mixed leagues. Today, I'm going to take a look at "sleepers" for deep AL-only and NL-only play, players who have an outside chance of potentially being useful in mixed leagues if things break the right way. These are guys who could shine a bit given some opportunity. We're talking "deep" sleepers here. Only a couple of these players are pretty much guaranteed a regular job.