The New England Patriots rarely, if ever, carry three quarterbacks on their active roster. They had Tom Brady, Jimmy Garoppolo, and Jacoby Brissett in the fold in 2016, but Brady was suspended to start that season, so that's why they kept the two young guns around.
Aside from that, keeping three quarterbacks has been an anomaly. But the Patriots signed former Cleveland Browns, Jacksonville Jaguars, and Philadelphia Eagles quarterback, Cody Kessler, last week to provide depth at quarterback. And it doesn't seem that he's going anywhere at least in the near future.