In the case of Shaun Marcum, since he was a reliever at times last year, and then made the transformation to the starting rotation, he is still eligible to play on Yahoo at the reliever spot as well as the starting pitching position. Next year though, he will probably only be able to be used as a starting pitcher. You can use him if you wish at reliever for this season, and reap the benefits of him as an elite starting pitcher at the reliever spot, instead of getting a traditional relief pitcher. You can almost look at it as really a matter of you being able to hold another starting pitcher on your team, just with the ability of putting him at reliever.