Allen is set to sign a two-year, $4.1 million contract with the Bills, Adam Schefter of ESPN reports.
Allen has spent most of his career as a backup and played in three games for Detroit last season, going 0-for-2 on pass attempts. With Buffalo, he'll likely be the No. 2 QB behind Josh Allen and replace previous backup Mitchell Trubisky, who is expected to sign with Tennessee. Kyle Allen's contract could be worth up to $6.1 million with incentives, per Schefter.