As a senior, he earned Metro League Offensive MVP honors after registering 2,360 all-purpose yards, 48 receptions, and 24 touchdowns.

As a redshirt freshman, he earned the starting left cornerback job, registering 45 tackles, 10 passes defensed (sixth in the Pac-12 Conference), 2 interceptions and 3 forced fumbles.

[2][3] He finished his collegiate career with 38 starts in 40 games, 144 tackles, 7 interceptions, 25 passes defensed (tied for 10th place in school history) and 4 forced fumbles.

[6] His fall in the draft was speculated to be due to his performance at the NFL Combine, as teams deemed him too slow to play cornerback.

[8][9] As a rookie, he was ineligible to participate in organized team activities (OTAs) until the University of Oregon classes ended.

Throughout training camp, Mitchell competed for a roster spot as a backup cornerback against Sterling Moore, B. W. Webb, Tyler Patmon, and Dashaun Phillips.

[13][14] On October 13, 2014, the Bears elevated Mitchell to their active roster, but remained inactive as a healthy scratch for the last ten games of the regular season.

Throughout training camp in 2015, Mitchell competed for a roster spot as a backup cornerback against Alan Ball, Demontre Hurst, Al Louis-Jean, Sherrick McManis, Jacoby Glenn, Qumain Black, and Bryce Callahan.

Head coach John Fox named Mitchell the fourth cornerback on the depth chart to begin the regular season, behind Kyle Fuller, Alan Ball, and Sherrick McManis.

[19] On June 13, 2016, Mitchell was claimed off waivers by the Houston Texans, to replace rookie cornerback Richard Leonard who suffered a torn hamstring.

[26] On October 30, Nelson was activated to play against the Denver Broncos and Mitchell returned to a backup role behind Kenneth Acker.

On March 15, 2018, Mitchell signed a three-year, $12 million contract with the Cleveland Browns, reuniting with John Dorsey who was the general manager with the Chiefs.

Mitchell started the first four games of the season at right cornerback, before suffering a broken wrist in Week 4 against the Oakland Raiders.

In 2020, second-year player Greedy Williams was expected to be the starter at right cornerback opposite Denzel Ward, but was lost for the season with a nerve injury in his shoulder that he suffered midway through training camp.