The Buffalo Bills have traditionally kept two quarterbacks active under head coach Sean McDermott. The only time I can really remember the team having three active quarterbacks was during the 2017 season when Joe Webb was playing special teams. While he might have had a big impact on one snowy game, more often than not the Bills only carry two active quarterbacks.
During the 2018 season, for example, Buffalo had a rookie Josh Allen along with Nathan Peterman and Derek Anderson. However, since Allen’s ascension into the upper-echelon of NFL quarterbacks, the Bills have trended towards using one extra spot on the 53-man roster elsewhere.