2. Mike Tomczak
Back in 1985, Mike Tomczak went undrafted out of Ohio State and ended up signing with the Bears. He would go on to play for Chicago through the 1990 season, backing up Jim McMahon for that Super Bowl Champion team. Tomczak didn't play too often, although he did end up starting a total of 31 games during his stint with Chicago.
During those 31 games, Tomczak went 21-10 as a starter and threw for 6,247 yards, 33 touchdowns and 47 interceptions. He wasn't an All Pro by any means, but as a backup quarterback, he did just fine for himself and was around for several seasons because of the trust the team placed in his abilities.
1. Steve Walsh
Finally, we come to a guy who ended up having one of the best seasons by a Bears backup quarterback in team history, back in 1994 when he had to replace then-starter Erik Kramer, due to injury, in Week 4.
Walsh would go on to post an 8-3 record as the team's starter and even help lead the team to a playoff win over their division rival, the Minnesota Vikings. That season, he threw for 2,078 yards, 10 touchdowns and eight interceptions. Walsh went on to back up Kramer for one more year in 1995 before signing with the Rams.