The Giants completed a minor league deal with veteran outfielder Melvin Upton Jr. on April 12. Just over a week later, Upton will be on the shelf for multiple weeks.
Upton, 32, underwent surgery Friday morning for a torn ligament in his thumb. The injury occured in extended spring training.
Max Wildstein of HardballScoop.com was first to report the news. Andrew Baggarly of the Bay Area News Group confirmed the report through GM Bobby Evans.
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Upton is expected to miss a minimum of eight weeks.
In 2016, Upton hit 20 home runs and stole 27 bases in 149 games between the Padres and Blue Jays.
Upton has belted 164 home runs and stolen 300 bases in his 12-year career.