I don't know how you define elite, but Papelbon has had good numbers since leaving the Sox. He is not as good as he was in his prime, but he is still effective. Uehara had a freakishly great season in 2013. He was elite for that season, but Papelbon has a longer track record as a good reliever. Of course Koji started his MLB career at age 34 while Paps started at age 24. Both were elite in certain seasons. Neither one is the equal of Mariano Rivera, if that is the true measure of elite.
Papelbon stats