No, he is the 7th most powerful shinigami in all of Soul Society according to stat points, just below Yamamoto Genryuusai, Aizen Sousuke, Unohana Retsu, Kyouraku Shunsui, Byakuya Kuchiki, and Hitsugaya Toshiro, the weakest captain according to the official stat points, is Zaraki Kenpachi, with 390 / 600 points. He's actually considered to be one of the strongest captains in history. His health is just awful.