By placing Mitchell on the 40-man roster, the A's have protected him from the Rule 5 Draft, to be held Dec. 8 at the Winter Meetings in Dallas. The move also ensures Mitchell of his first invite to big league camp.
Mitchell enjoyed a breakout 2011 season in the A's organization, batting .355 at Double-A Midland before earning a July 3 promotion to Sacramento, where he posted a .302 average with 14 doubles, three triples, five home runs, 28 RBIs and 13 stolen bases in 56 games.
The 27-year-old outfielder, a former fifth-round Draft pick by the A's in 2006, recently underwent knee surgery and likely won't be ready by season's start, but it's likely he'll play a prominent role in Oakland's outfield mix once healthy.
Scribner and Hunter were both claimed off waivers from San Diego on Oct. 25. Their departure from the 40-man roster, combined with the addition of Mitchell, leaves the A's with one open slot.