With Jay Cutler's availability this week extremely questionable after he suffered a concussion Sunday night, the Bears signed free-agent quarterback Josh McCown on Tuesday as insurance.
If Cutler can't play, veteran Jason Campbell will start Monday night at San Francisco, with McCown as the only backup.
McCown, 33, has started 33 NFL games and has played in 50 overall in stints with Arizona (2002-05), Detroit (2006), Oakland (2007), Carolina (2008-09) and the Bears (2011).
The 6-foot-4, 213-pounder from Sam Houston State has played in just six games since 2008, but three of those came last season with the Bears. That included two starts after he was signed late in the season.
McCown was 1-1 as a starter for the Bears after he replaced Caleb Hanie, who failed as the fill-in after Cutler suffered a season-ending fractured thumb in Week 10.
Despite his commendable performance, McCown was cut in training camp this year as the Bears elected to go with just two quarterbacks, Cutler and Campbell, on the 53-man roster. Undrafted rookie quarterback Matt Blanchard of Lake Zurich is on the practice squad.
McCown's passer rating in his two starts last season was 76.1, compared to Hanie's 41.8 and Cutler's 85.7.
McCown entered the NFL as the Cardinals' third-round pick (81st overall) in 2002. He has completed 645 of 1,113 (58.0 percent) pass attempts for 6,998 yards, 37 touchdowns and 44 interceptions for a 71.2 passer rating.
In three games last season he completed 35 of 55 (63.6 percent) passes for 414 yards, 2 touchdowns and 4 interceptions.
Tight end Brody Eldridge was waived to create roster space for McCown.