Mathis, who sprained the medial collateral ligament in his left knee Sunday, will be eligible to practice in six weeks and to play in eight weeks. He would be allowed to play in the Eagles' Nov. 10 game against the Carolina Panthers.
To take their spots, the Eagles signed veteran offensive lineman Wade Smith, linebacker Emmanuel Acho and offensive lineman Kevin Graf. Acho and Graf were on the Eagles' practice squad after spending all of training camp with the team.
The 6-foot-4, 295-pound Smith has 11 years' experience with four teams. He was named to the Pro Bowl after the 2012 season. Smith, 33, started 64 consecutive games at left guard for the Texans.
It isn't clear whether Smith can step right in and start for the Eagles when they play the Indianapolis Colts on Monday night. If not, the Eagles could start Dennis Kelly, who made 10 starts for them in 2012.
Andrew Gardner is expected to start at right tackle for Barbre, who was the replacement for suspended starter Lane Johnson. Gardner played well in the second half of Sunday's victory over Jacksonville.
Goode played only on special teams Sunday. He was expected to give inside linebacker DeMeco Ryans the occasional rest. That role will likely go now to Acho or to Casey Matthews. Acho was in training camp with the Eagles in 2013, was on the New York Giants' practice squad for the first half of the season and on the Eagles' 53-man roster from then on. Acho appeared in six games with the Eagles, primarily on special teams.
Graf went undrafted after playing at USC. He signed with the Eagles as a free agent in May. He could fill the role intended for Matt Tobin, who was in line to be the primary backup at guard and tackle until he sustained a high ankle sprain in the last preseason game. Tobin is at least two weeks away from returning.