He began the season on the bench but eventually earned his first career start in the second game against Pittsburgh, a 16-10 OT victory.

In a week 10 matchup against Eastern Michigan, he made his first career interception in the fourth quarter that led to the game-winning touchdown.

The Bobcats played Central Michigan in the MAC Championship, with Mitchell shifting over to strong safety and ending the game with 6 tackles and an interception.

After sitting out week 11 against Bowling Green with an injury, he returned the next game against Akron; Mitchell made 9 tackles in the 49–42 victory.

[8] The Oakland Raiders' selection of Mitchell was highly scrutinized by the analysts and drew an uproar among fans at Radio City Music Hall.

[9][10] NFL analyst Mike Mayock graded him in the seventh round and Mel Kiper Jr. stated that the Raiders could've possibly signed him as an undrafted free agent.

I had him between 40 and 73 at safety, with a seventh-round grade,” -Mel Kiper Jr.Mitchell was the highest Ohio player to be drafted since Gene Ruskowski's fifth-round selection (44th overall) by the Los Angeles Rams in 1948.

[16][17] He began training camp competing with veteran Michael Huff for vacant strong safety job left by the departure of Gibril Wilson.

Head coach Tom Cable named Mitchell the backup strong safety to Tyvon Branch who won the job after emerging as the top option in training camp.

On December 12, 2010, he intercepted his first career pass from Jaguars' quarterback David Garrard and made two solo tackles during the Raiders' 31–38 loss.

[22] He returned in Week 4 and made one tackle and sacked New England Patriots' quarterback Tom Brady, as the Raiders lost, 19–31.

During a Week 12 matchup against the Chicago Bears, Mitchell earned his first start of the season and recorded two tackles in a 25–20 win.

On December 11, 2011, Mitchell made his third consecutive start of the season against the Green Bay Packers and intercepted a pass from Aaron Rodgers while making four solo tackles during the Raiders' 16–46 loss.

[23] The Oakland Raiders did not qualify for a playoff berth after finishing 8-8 and head coach Hue Jackson was fired by Mark Davis at the end of the season.

Mitchell remained the backup strong safety to Tyvon Branch under head coach Dennis Allen to begin the 2012 season.

On November 18, 2012, Mitchell started his first game of the season against the New Orleans Saints and finished the 17–38 loss with a career-high 11 tackles.

During a Week 14 contest against the Denver Broncos, he earned six solo tackles and sacked Peyton Manning, as the Raiders lost, 13–26.

[16][24] He competed with Charles Godfrey, D. J. Campbell, and Anderson Russell throughout training camp for the job as the starting strong safety.

He played in his first game during a Week 2 match-up against the Buffalo Bills after Godfrey suffered a season-ending injury and made three solo tackles in his place.

[16][28] Entering training camp, he was the expected starting free safety, replacing Ryan Clark, who left for the Washington Redskins during the off-season.

In Week 8, he intercepted Bengals' quarterback Andy Dalton and returned on for 7 yards, while also finishing the loss with five combined tackles.

Mitchell was later involved in another controversial hit when he delivered a low tackle to the back of quarterback Alex Smith's legs, well after the ball was thrown.

Mitchell received widespread criticism from fans that deemed it "as dirty as it gets", "unnecessary", "egregiousness", and Smith later commented that it was, "as flagrant as it gets".

[35] In the wild card round of the playoffs against the Houston Texans, Mitchell suffered a calf strain and was placed on injured reserve on January 9, 2019.