Forston had three tackles in three games for the Patriots last season. Williams had no catches in two games.
The Patriots originally signed Forston in May 2012 as an undrafted free agent from Miami. He played one game and spent most of that season on the team's practice squad.
Williams was drafted by the Green Bay Packers in the fifth round in 2011 and had nine catches in 26 games for them over two seasons. He started last season with Jacksonville, where he played seven games before being cut and signed by New England.