According to ESPN's ...According to ESPN's Adam Schefter, San Francisco 49ers quarterback Brock Purdy (shoulder) is anticipated to play in Sunday night's matchup versus the Bills. The signal-caller wasn't on the field for the Week 12 loss to the Packers. As a result, Brandon Allen got the start, finishing with 199 yards, one touchdown, and one pick off 17-for-29 passing. If Purdy is officially cleared to suit up on Sunday, he could have a tough time getting it going, considering heavy snow is in the forecast for Buffalo. Still, he should at least be considered a starting fantasy option in multi-QB setups. But if Purdy isn't out there, Allen doesn't have much upside in any format.
Source: https://www.rotoballer.com/player-news/brock-purdy-expected-to-suit-up-versus-buffalo/1507305