Via STACKSan Antonio Spurs power forward Tim Duncan, arguably one of the 10 best players to ever step foot on an NBA court, retired today. That's a strange statement, one we've be waiting to write for what feels like a decade, yet Duncan just kept chugging along. His hair got grayer, his stride a little slower, but the Big Fundamental remained effective until the very end, when he was relegated to the bench in the Spurs' matchup against the Oklahoma City Thunder in the 2016 Western Conference Semifinals. At age 40, after 19 years in the NBA, Duncan finally decided it was time to go. His decision only makes his longevity more impressive. The big man was still playing 30 minutes a game as recently as two seasons ago. And yet, consistent with Duncan's quiet personality,we never heard much about how he kept himself going, how he handled the extra mileage that comes with making the playoffs in every single season of his career. But when you do a little digging and learn more about Duncan's strict attention to both his training and his diet, it's easier to understand how he lasted so long playing one of the most physical positions in the game for almost two decades. Between the 2012 and 2014 seasons, he lost a good 20 pounds, as he participated in intense workouts that included swimming, sand running, tire flipping and boxing, the last of which he spent much of the 2012 off-season doing with fellow center Roy Hibbert. He was known for beginning his off-season workouts at the Spurs' practice gym in July, a month before the doors were opened to the team. To relieve pressure on his legs and knees, Duncan also changed his diet as he approached his mid-30s. "He lost a lot of weight," former teammate Bruce Bowen said in 2012. "In fact, when we would go out to eat, Tim would split the bill and we had a big plethora of food out of us. But now, he's starting to eat wheat bread and chicken only, no mayonnaise, no mustard, none of that." Duncan also cut down on sugar and bread consumption as he got older, and he stopped snacking late at night. We may not know Duncan's exact diet, but it worked well enough that Al Jefferson, who just signed with the Indiana Pacers, credits Duncan for influencing him to lose weight to prolong his career down in the post. "I had to get the pressure off my knees, man," Jefferson told SB Nation last year. "Tim Duncan set a great example. He lost his weight, he got down, and he's 38 or 39 still playing at a high level. I just turned 30, and it was time to add some years to my career, man. I've still got a lot of ball to play." As Duncan leaves the game behind after his Hall of Fame career, countless athletes will look to his legacy for guidance on how to extend theirs. They'll just have to do some serious research to find it.