Mitchell played in the NFL for the Dolphins, Detroit Lions, Baltimore Ravens and Cincinnati Bengals, as well as the Orlando Thunder of the World League of American Football.
[3] He served as Dan Marino's back-up for three seasons but found most of his time spent with the Orlando Thunder of the NFL Europe in 1992 as a volunteer.
That year, he joined a lawsuit with twelve other players (most notably involving Freeman McNeil and Marcus Allen) in an antitrust suit against the NFL that saw unrestricted free agency soon come to the league.
Mitchell became the Dolphins' starting quarterback in 1993 when Marino ruptured his Achilles tendon in week 6 at Cleveland that saw him miss the rest of the season.
[6][7] Mitchell joined a Detroit offense that included running back Barry Sanders and receivers Herman Moore and Brett Perriman.
In a loss to the Green Bay Packers, Mitchell went down with an injury, and was replaced by backup quarterback Dave Krieg, who led the team to the 1994 playoffs.
Offensive tackle Lomas Brown, on ESPN program First Take later admitted to purposefully missing a block that resulted in this injury, as he was upset over Mitchell's poor play.
Facing the Tampa Bay Buccaneers, he went 10-of-25 for 78 yards and an interception before being knocked out with a concussion in the third quarter (where Frank Reich replaced him) in a 20-10 loss.
Made expendable after the Lions signed Gus Frerotte two weeks earlier, Mitchell was dealt to the Baltimore Ravens on March 16, 1999, for a third-round draft pick that year and a fifth-rounder in 2000.
"[11][12][13] After not being able to acquire Brad Johnson from the Minnesota Vikings,[14] the Ravens settled for Mitchell who signed a one-year $3 million contract upon his arrival in Baltimore.
[22] Mitchell has since tried to manage his weight and health, which saw him weigh 418 pounds in 2023; in January 2024, his kidneys shut down and he developed blood clots in his lungs but he eventually made a recovery.