The Spurs will hold Manu out of the lineup longer than actually needed, fall down the standings, win the lotter and draft Anthony Davis.
Davis takes over for Duncan, Kawhi takes over for Bowen, they pull two European/South American players out of their ass and, boom, another dynasty is born.
Seriously though, he shouldn't miss too much time. I doubt this results in the Spurs missing the playoffs and Gino will likely be back in the lineup by the end of the month. They may not be able to contend for the top seed in the West, but really, the West is so tight that seeding is much less important than the matchup you will get in the 1st round.