Williams, 26, spent the 2016 season on injured reserve with a torn ACL.
The 6-foot-6, 304-pound Williams originally entered the NFL as a seventh-round draft pick by the Detroit Lions in 2013 out of Alabama. He spent his rookie season on injured reserve and the 2014 season on the Lions' practice squad.
Williams was acquired by New England from Detroit in a trade on Aug. 26, 2015, appearing in 15 regular-season games (nine starts) that season, with three receptions for 26 yards. He also played in two playoff games with one start and his primary contributions came as a blocker.
The candidates now competing for the No. 3 tight end spot on the team are James O'Shaughnessy, Matt Lengel, Rob Housler and rookie Jacob Hollister.
O'Shaughnessy may be the favorite to get the final spot entering the offseason training program. The Patriots traded their 2017 fifth-round pick to the Kansas City Chiefs for O'Shaughnessy and a sixth-round pick. He has eight career receptions for 86 yards.