"It's not major, just don't want to risk it right now," Green said, according to the San Antonio Express-News' Tom Orsborn.
The 30-year-old has long operated as one of the NBA's more established three-and-D threats, but his reputation has taken a hit over the past two seasons—namely because his efficiency from beyond the arc has dipped.
After making at least 41 percent of his threes in four straight seasons from 2011-12 to 2014-15, Green's production fell off a cliff in 2015-16 when he shot a full-season career-worst 37.6 percent from the field and 33.2 percent from three.
Those struggles carried over to last season, when Green averaged 7.3 points on 39.2 percent shooting from the floor and 37.9 percent from distance.
Now in the third season of a four-year, $40 million deal he signed prior to the 2015-16 season, Green has looked rejuvenated as he's averaged 11.1 points, 3.7 rebounds and 1.0 steals per game on 43.7 percent shooting from the field and 38.9 percent shooting from deep.
With Green out and Manu Ginobili on a rest day, per McDonald, it will be on Bryn Forbes to pick up the slack on the wing.