ESPN's Adrian Wojnarowski reported that the early indication is Anderson has an MCL strain. He will receive an MRI on Monday.
Anderson landed awkwardly in the third quarter while attempting a layup. Joffrey Lauvergne replaced him in the San Antonio lineup, and the Spurs confirmed Anderson will be out for the remainder of the game.
The 24-year-old is on pace to have a career year in the NBA, showcasing the all-around game that led San Antonio to select him with the 30th overall pick in the 2014 draft.
Entering Sunday, Anderson was averaging 9.0 points, 6.1 rebounds and 3.0 assists. He was also shooting 36.4 percent from beyond the arc.
While Anderson isn't one of San Antonio's most important players, his absence further depletes what is already a shorthanded frontcourt with Kawhi Leonard yet to make his 2017-18 debut.
Rudy Gay is an obvious replacement for Anderson at small forward, but moving Gay into the starting lineup would mean needing somebody to step up off the bench to spell LaMarcus Aldridge at the 4. Lauvergne will likely be the biggest beneficiary in terms of playing time should Anderson's injury leave him out for an extended period of time.