The Bears took advantage of the cap loophole last year when they signed Mike Green to a five-year extension.
Mitchell, who is now signed through 2008, has started at left tackle in nine of Chicago's last 10 games and is one of three Bears offensive linemen to start all seven games this season.
The third-year man began his career in Chicago on the practice squad, signing with the team on Sept. 16, 2003 after being waived by the Cleveland Browns. Mitchell entered the NFL as an undrafted free agent signing with Cleveland out North Carolina A&T in 2002. He spent his rookie season on injured reserve due to a lung injury.
In order for Peterson to make the 53-man roster he has had to develop into a special teams contributor. Coming off a personal-best six special teams tackles last week versus San Francisco, Peterson currently leads the squad with a career-high 12 special teams tackles this season.
A sixth-round draft choice (199th overall) out of Georgia Southern in 2002, Peterson has career offensive totals of 171 rushing yards on 41 carries (4.2 ypc) and four receptions for 23 yards while playing in 20 career games with one start.
Peterson would have been a restricted free agent at the end of the season, but the extension means he's signed through 2006.