he wasnt even in the story for that long and by that time he was already 72 years old. he was able to permanetly scar a SANNIN. he had stated himself that his chakra reserves had greatly deplenished since his youth.in a flashback he could have killed orochimaru with ease because of his experimentations on other leaf ninja but chose to let him live. i doubt minato would have even posed a threat that age. his trump card is speed and by that time it would've greatly decreased. in narutopedia it stated that hiruzen was a MASTER of genjutsu, ninjutsu, and taijutsu.
Quote from narutopedia,"Hiruzen Sarutobi, the Third Hokage, was
said to be the strongest Hokage in the village's history, as well as strongest of the Five Kage of his era." HAHA