Jean-Gilles was hurt late in the first half when he was hit from behind by the Cardinals' Chike Okeafor, who was trying to make a diving tackle of quarterback Donovan McNabb.
A fourth-round pick in 2006, Jean-Gilles was starting for two-time Pro Bowl guard Shawn Andrews, who hasn't played since hurting his back in Week 2.
Eagles coach Andy Reid said Jean-Gilles' injury was similar to the one sustained by Andrews in his rookie year in 2004. Andrews was hurt in the season opener that year and missed the rest of the season.
Nick Cole, who signed with the team as a rookie free agent in 2006, replaced Jean-Gilles in the lineup.