Green exited less than 30 minutes into practice and was wearing an ice wrap around his left leg as he walked to the locker room.
Bills coach Chan Gailey used words such as "tweaked" and "precautionary" to describe Green's injury and said he expects the 6-foot-6, 315-pound tackle back soon.
The team is off Sunday.
Green, who spent three years with Oakland before signing a three-year contract with the Bills this year, entered the NFL in 1999 as an undrafted free agent with Atlanta. He has 46 starts in 89 career games, having also played for Tampa Bay and Denver.