49ers key matchup No. 1: Colin Kaepernick vs. Jason Campbell

This is the final part in a series that spotlights three 49ers-Bears matchups to watch Monday, 5:30 p.m. (ESPNCBS 5), at Candlestick Park.49ers QB Colin Kaepernick vs. Bears QB Jason CampbellTale of the tape
Kaepernick (7): 6-foot-4, 230 pounds, second season, Nevada
Campbell (2): 6-foot-5, 230 pounds, eighth season, AuburnJason Campbell has 70 career starts on his resume in six previous seasons with the Washington Redskins and Raiders.Colin Kaepernick is slated to make his first NFL start.MAIOCCO: Key matchup No. 2 -- Crabtree vs. TillmanWhen the 49ers face the Chicago Bears on Monday night, it will likely be a game that comes down to the quarterbacks. It might be the quarterback who makes the most plays. Or, more likely, the difference could come down to the quarterback who simply avoids the major mistake.In what figures to be a low-scoring game, it might not take much to turn the game. The 49ers own the league's third-ranked defense, while the Bears' defense is No. 5.The 49ers' defense leads the NFL with just 14.1 points allowed per game. The Bears are generating turnovers at a rate of 30 takeaways in nine games."Obviously, they're a great defense," Kaepernick said last week when it appeared as if Alex Smith was on track to make the start after being asymptomatic and taking part in four days of practices."I think they're No. 1 in the NFL right now," Kaepernick added. "A lot of turnovers, a lot of great players on that side of the ball who have a lot of Pro Bowls, as far as (Brian) Urlacher, (Lance) Briggs, (Julius) Peppers. They have a lot of great players over there. We're going to have our work cut out for us."Campbell takes over for Jay Cutler, who was ruled out of action on Friday due to a concussion he sustained Nov. 11. Kaepernick is scheduled to start in place of Smith, who sustained a concussion in the second quarter of last week's game against the St. Louis Rams.MAIOCCO:Key matchup No. 3 -- Justin Smith vs. Chilo RachalThe 49ers announced Monday morning that Smith has been declared out for Monday's game after being evaluated by team medical director Dr. Dan Garza. Smith had been cleared to participate in practices Wednesday through Saturday.Second-year player Scott Tolzien, who has suited up for just one game in his career, will serve as the 49ers' backup quarterback.Campbell enters Monday's game with a lot of NFL experience. In 19 starts with the Raiders the past two seasons, Campbell posted an 11-7 record as a starter. He sustained a broken collarbone last October, leading the Raiders to trade for Carson Palmer. Campbell did not play again last season, and he signed with the Bears in the offseason."We felt like we needed to improve our backup quarterback position in the offseason," Bears coach Lovie Smith said. "So we felt real good about being able to convince Jason to come here and be Jay's backup."This season, Campbell has completed 12 of 20 passes for 94 yards with no touchdowns and no interceptions. He entered last week's game against the Houston Texans at halftime. Campbell led seven possessions, during which time the Bears managed only four first downs, one field goal and one missed field goal.Kaepernick has seen action in six games this season, including consecutive games against the New York Jets, Buffalo and New York Giants as a change-of-pace quarterback. He has completed 16 of 26 attempts for 206 yards. He is the 49ers' third-leading rusher with 177 yards on 21 attempts.Lovie Smith said last week that his Bears defense would prepare for both Alex Smith and Kaepernick."Colin has been playing some anyway, so we've been preparing for that anyways," Lovie Smith said. "Again, we don't change what we do an awful lot based on change in the quarterback. Both of those quarterbacks have played some for them."