But that wasn't the question. The question was "Is he closer to Rivera than he is to Papelbon"?
At age 30, Kimbrel has been worth 19.1 fWAR
At age 30, Rivera was worth about 12 fWAR. But he also only had 4 seasons as a closer under his belt and fWAR numbers from the 1990's might be incomplete. Through his first 9 seasons (same number as Kimbrel )as a closer, Rivera was worth 17 fWAR.
At age 30, Papelbon was worth 14.2 fWAR by age 30 and 18.8 fWAR through 9 seasons as a closer.
To me, Kimbrel looks a lot like Papelbon 2.0, and as the future is unknown, using a close parallel is one way to try to evaluate it. (It's actually the basis of the entire PECOTA projection system.)