To reach 61-21, the Spurs only have to go 7-5 over the remaining 12 games. That guarantees them the second best record in the league, and home court over everyone except GSW. Other than trying to catch GSW for the best record and the 1 seed, there's no point in trying for better than that. But I would hate to see them go into the playoffs on anything worse than 7-5. I like your prediction: 61-21.