Siliga will be joining his fifth team since entering the NFL as an undrafted free agent out of Utah in 2011. He appeared in eight games with the Tampa Bay Buccaneers in 2017, registering eight tackles.
The 6-foot-2, 345-pound Siliga spent three of his six seasons with the New England Patriots, appearing in 25 games and making 13 starts. He had a career-best 44 tackles in 2014 in helping the Patriots win the Super Bowl.
In 44 games with the Denver Broncos, Patriots, Seattle Seahawks and Buccaneers, Siliga has posted 114 tackles and 6.5 sacks.
In a corresponding move, Jacksonville waived defensive tackle Kaleb Eulls with an injury designation.