There are a variety of reasons why NBA players end up retiring and leaving the game of basketball earlier than expected. For some, injuries cut promising careers short. For others, age catches up to them or they lose the passion needed to compete at the sport's highest level.
Injuries are perhaps the most common factor leading to early NBA retirements. The physical toll of playing 82 regular season games, plus playoffs, can simply become too much. Knees, ankles and backs take a pounding. Even a single severe injury like a torn ACL can end a career. Brandon Roy and Yao Ming are examples of stars who saw their playing days shortened due to mounting injury issues.
Age and declining athleticism also force many to retire by their mid-30s. The average NBA career length is just 4.8 years. Staying dominant into a player's late 30s is extremely rare. Stars like Dwyane Wade and Dirk Nowitzki retired around age 38, feeling they no longer had the speed and stamina to compete against younger talent.
Losing the drive and passion to play is another reason for retirement. After a decade or more on the court, some may just feel ready to move on to other opportunities and challenges. There's also the mental fatigue that sets in from the constant travel, practices, recovery and pressure to perform over many years.
While a select few like Vince Carter played into their 40s, the typical NBA retirement age is somewhere in the mid-30s. Injuries, age and burnout all contribute to cutting careers shorter than expected for most players.