Watch the Spurs' beautiful tribute video for Tim Duncan

Five-time NBA champion Tim Duncan is retiring from the game of basketball at the age of 40. The Spurs announced Monday that Duncan has decided not to return for what would be a 20th NBA season in 2016.

Duncan was overlooked by fans outside San Antonio for his entire career, but he very well may have been the best player of his generation. Duncan made 15 All-Star teams and was named to the All-NBA first team 10 times, just one shy of Kobe Bryant and Karl Malone. Over the course of Duncan's career, the Spurs never won fewer than 50 games in a non-shortened season, and he took the Spurs to the Western Conference Finals nine times. The team released an emotional tribute to Duncan on Twitter Monday, and it just might make Spurs fans cry.