It's tough to call on Papelbon likes others are touting, given his experience. I would think that Francona would try to put Papelbon in stressful setup situations during the season to test his nerves. If he gets outs or doesn't allow too many inherited runs to score, I think Francona's confidence will increase. He'll leave Timlin in his comfortable role and go with Papelbon.
However, what if Papelbon falters? Then it might be Timlin for the short term until Hansen comes up. The Sox may not like Timlin as closer but hey, he gets the job done.
'Idiot', I think you should take your chances and try to acquire Papelbon just in case. I think Papelbon will do fine this year..