Pace missed much of the previous two seasons with injuries, including all but one game in 2007 with a shoulder injury. He has missed just one of the Rams' 10 games this season, but he was ruled out of Sunday's game after going to the locker room during the second quarter.
St. Louis also lost right guard Richie Incognito to a strained rotator cuff just before halftime, and cornerback Ron Bartell also was ruled out with a torn meniscus in his knee during the Rams' disastrous first half in a 35-16 loss to the 49ers.
Pace was replaced by versatile backup Adam Goldberg, while Brett Romberg replaced Incognito. All three injured players will undergo MRI exams soon.
Linebacker Pisa Tinoisamoa injured his ankle, and fellow linebacker Will Witherspoon hurt his leg. Interim coach Jim Haslett didn't think either injury was serious.
Copyright 2008 by The Associated Press