Kaepernick was outstanding in his first career start, completing 16 of 23 passes for 243 yards and two touchdowns as the Niners rolled to a 32-7 victory.
San Francisco made life difficult on Monday for Campbell, who was sacked six times and threw two interceptions.
According to the Elias Sports Bureau, the last time two quarterbacks made their first start of the season against each other on MNF (other than Week 1) in a non-strike season was 1979 when the Rams' Vince Ferragamo and Falcons' June Jones faced each other in Week 12.
Smith, who is ranked third in the NFL with a 104.1 passer rating, practiced in a noncontact black jersey last week and took part in most of the drills involving the first-team offense.
Smith, who has made 28 consecutive starts, was injured during the first half of a 24-24 tie with the St. Louis Rams in Week 10 and left the game midway through the second quarter.
Information from The Associated Press was used in this report.