Already minus quarterback Chris Chandler, the Chicago Bears discovered on Saturday that they will face the Arizona Cardinals on Sunday without another backfield starter because tailback Anthony Thomas has been ruled out of the game with viral pneumonia.
The team's leading rusher, Thomas has 168 attempts for 721 yards and four touchdowns despite missing two games because of a foot injury. Rookie Brock Forsey, a sixth-round draft choice from Boise State, will make his second start.
Forsey has carried 20 times for 61 yards and one touchdown. In his previous start, against Detroit on Oct. 26, Forsey rushed for 56 yards on 19 carries.
Chicago officials had hoped that Thomas, the league's offensive rookie of the year in '01 when he ran for 1,183 yards, would respond to treatment for the infection. But despite treatment Friday evening, the third-year veteran and former Michigan standout was still in discomfort, and club physicians determined he would not be able to play.
The team's No. 2 tailback, Adrian Peterson, is already on injured reserve for the balance of the season with an ankle injury. Chicago will be without Chandler, who has soreness in his right shoulder after an injury last week, and Kordell Stewart will start at quarterback versus the Cardinals.
Stewart opened the season as the starter but lost the job to Chandler after five games.
Thomas slumped last season, rushing for 721 yards, which put his future with the franchise in doubt. But the back dubbed the "A-Train" regained his form about a month into the season, and Thomas has posted three 100-yard performances and five games of 90-plus yards.
Team officials are confident Thomas will be fully recovered by next week.
In other Bears news, the club on Saturday placed rookie tight end Robert Johnson on the injured reserve list with a fractured foot. To replace him, the Bears signed tight end Gabe Reid off the Tennessee Titans practice squad.
Len Pasquarelli is a senior writer for ESPN.com.