Anderson, who turns 30 on Dec. 30, was claimed off waivers from National League West rival Colorado on Oct. 30 and is recovering from surgery on his left knee that derailed his 2019 season. He went 0-3 with an 11.76 ERA in five starts spanning 20⅔ innings after making 32 starts in 2018.
Once healthy, Anderson is expected to compete for a rotation spot. The 2011 first-round pick hopes to be ready by spring training. He has planned to rehab in Scottsdale, Arizona, where the Giants have their spring training complex.
San Francisco could lose 2014 World Series MVP and longtime lefty ace Madison Bumgarner in free agency this offseason.