7. Brandon Roy
Brandon Roy has one of the most bittersweet career arcs in NBA history. When he was good, he was really good. Roy was the 2006-07 Rookie of the Year, made three straight all-star games from 2008 to 2010, made back-to-back all-NBA teams in '08-09 and '09-10, and earned MVP votes in the '08-09 season after averaging 22.6 points, 4.7 rebounds, 5.1 assists and 1.1 steals with 48/38/82 shooting splits.
However, nagging knee injuries cut the 6-6 guard's career short. He was forced to retire following the 2010-11 season and only played five games in 2012-13 when he tried to make a comeback with the Minnesota Timberwolves.
Had Roy been able to stay healthy and play more than five seasons in Portland, his PER of 20.1 would likely be much higher.