Carter, 26, was a fourth-round pick of the Colts back in 2011. He would spend two years with the Colts before later being traded to the Ravens in return for WR David Reed. However, he would last just a few days with Baltimore before being cut loose.
The Jaguars signed him back in December of last year. He had a base salary of $645,000 for the 2014 season.
Nevis, 25, was also taken by the Colts in the third-round of the 2011 draft class. He spent two years with the Colts before being cut loose and bouncing around with the Chargers, Cowboys and Jaguars last year.
Last year, he appeared in 12 games and totaled 11 tackles.
Williams, 27, signed with the Arizona Cardinals as an undrafted free agent out of Toledo back in 2010.
He signed with the Seahawks in January of last year, but was later released in October, and subsequently claimed off of waivers by the Jaguars.
In 2013, he appeared in 6 games, but never registered any offensive statistics.