Purdy (shoulder), who is listed as questionable for Sunday's game against Buffalo, didn't have any setbacks Friday or Saturday and is expected to start against the Bills, Adam Schefter of ESPN reports.

Purdy's shoulder issue caused him to miss last Sunday's loss to Green Bay, but after getting in some light throwing at the start of this week, he logged a full practice Friday. He appears to have responded well to that session, and with no subsequent setbacks, the star quarterback appears set to return to the field Sunday. Purdy's presence is clearly a big boost to San Francisco's air attack, as No. 2 quarterback Brandon Allen completed 17 of 29 pass attempts for 199 yards, one touchdown and one interception while starting in place of Purdy in a Week 12 loss to the Packers. However, both the 49ers and Bills could face a challenge on offense -- and specifically in the passing game -- Sunday with the forecast calling for wind and frigid temperatures along with potential snow.