1st post here.
Papelbon, I believe, was prepared Spring Training as a starter and replace Foulke in the first week of the season as their closer. Personally, I like Papelbon as a closer but remember that he had some good starts last year for the Sox. He could go either way but for most, if not all this season, he'll probably remain their closer.
Hansen is trained/drafted to become Boston's future closer. He's on their 40 team roster and is currently in a $4mil/4year deal. IMO, he'll most likely be their closer next season.
Another potential starter is Jon Lester. With Wells aging and injured he could possibly replace him in the future.
Those are basically the three big names for BoSox pitching prospects. I hope Lester stays in the big leagues for another start and that Boston recalls Hansen up soon.