Fig 6.

Assessing the relationship between age at time of injury and the change in player performance before and after injury. Principal component analysis was used to analyze the change in performance 1 season before injury with 1 season after injury of the following: number of games played, number of touchdowns, number of interceptions, QBR, completion percentage, and number of passing yards. Change in performance metric was determined by normalizing the metric from the first season after injury to that from the season before injury (P = .048) (QBR, quarterback rating.)