The 75 greatest players in NBA history, ranked by Player Efficiency Rating (PER)

58.    Dan Issel-20.99

Hall of Fame center Dan Issell is one of the few players in basketball history to split his career between the ABA and NBA and be a star in both leagues. Issel spent the first six seasons of his career with the Kentucky Colonels before joining the Denver Nuggets, where he proved to be a superstar, averaging 25.6 points and 9.1 rebounds. The Nuggets were later absorbed by the NBA and Issel became an immediate star, even making the all-star team in his first season.

While he would only make one all-star team in his ten seasons in the NBA—all with the Nuggets—he still put up terrific numbers, averaging 20.4 points on 57.2% true shooting and 7.9 rebounds and boasting a PER over 21 in eight of those ten seasons.

That relatively short NBA career ironically helps him since he didn't go through a prolonged decline. On the other hand, most of his best seasons happened to be in the ABA. There, he put up monster numbers, including leading the ABA in scoring three straight years and scoring more than 2,000 points over four consecutive seasons. Had those seasons been counted, he'd be several spots higher.