Signing Papelbon was a desperation move for the Phillies. They've depleted their farm in big trades, and have overextended their payroll. They want a championship, and their window is closing. So, they filled their biggest hole with the best guy available... even if it will cripple their team in years to come, and probably prevent them from resigning Cole Hamels.
Seriously, if you have to chose between Hamels and Papelbon, is it any contest?