Mitchell began the 2010 season with the Trenton Thunder of the Class AAEastern League.[10] On August 21, 2010, Mitchell was promoted from Trenton to the Class AAAScranton/Wilkes-Barre Yankees of the International League.[11] Before the 2011 season, Mitchell was rated the organization's 18th best prospect and 10th best pitching prospect.[12] In 2011, he had a 13–9 win–loss record with a 3.18 ERA for Scranton/Wilkes-Barre. For this performance, Mitchell won the 2011 Yankees' Minor League "Pitcher of the Year" Award.[13]
Mitchell was added to the Yankees 40-man roster after the 2011 season to protect him from the Rule 5 draft.[14] Competing for the long reliever role with the Yankees in spring training in 2012,[15] the Yankees chose David Phelps for the role, and Mitchell was optioned to Scranton/Wilkes-Barre.[16]
On April 29, 2012, Mitchell was recalled to the Yankees after Freddy García was moved to the bullpen.[17]David Phelps was placed in the rotation, Cody Eppley was optioned to Scranton/Wilkes-Barre, and Mitchell took Phelps' role of long relief.[18] He made his major league debut on May 1, 2012, against the Baltimore Orioles, allowing two hits and striking out one in an inning of work.[19] He made three more appearances with the Yankees.[20]
Seattle Mariners
The Yankees traded Mitchell and pitcher Danny Farquhar to the Seattle Mariners for Ichiro Suzuki on July 23, 2012.[21] Mitchell was optioned to Triple-A Tacoma after the trade and pitched to a 2.96 ERA in eight starts. On April 11, 2013, Mitchell was designated for assignment.[22] After clearing waivers, he opted for free agency.[23]
New York Mets
Mitchell signed a minor league contract with the New York Mets on April 22, 2013.[24] He pitched to a 7.71 ERA in 81.2 innings out of the bullpen and starting rotation. Mitchell became a free agent after the season.
On August 1, 2016, Mitchell was traded to the Long Island Ducks for former major league player Sean Burroughs.[20] He became a free agent after the 2016 season.