While the 70-year-old signed a three-year contract extension in April, he’s also widely known to be taking a year-by-year approach to this stage of his storied career. As of now, a source said Popovich has given no indication to the organization that he won’t be back next season. Yet whenever he steps away, whether it’s after he coaches Team USA in the Tokyo Olympics this summer or sometime thereafter, there’s one name that continues to come up from league sources as a possible replacement: Bill Self, the longtime Kansas coach and close friend of Spurs general manager R.C. Buford.