McClain, 25, aggravated a groin injury last week against the Texans. He originally injured his groin during Week 2 against the Tennessee Titans and missed Dallas' Week 3 game against the St. Louis Rams.
McClain, in his first season with the Cowboys, has 23 combined tackles, one sack and one forced fumble in four games. He was the No. 8 pick in the 2010 draft by the Oakland Raiders out of Alabama. He did not play during the 2013 season and has retired twice.
Dallas is 21st in yards allowed per game after finishing last in the league in 2013.
The Cowboys are 4-1 and play the Seahawks in Seattle on Sunday at 4:25 p.m. ET.
- Paul Palladino