According to ESPN's Andrew Marchand, Ackley has a herniated disk.
Ackley, who arrived in New York just last week after being traded from the Seattle Mariners, has not yet started a game with the Yankees. He went hitless in three at-bats against the Chicago White Sox over the weekend.
The 27-year-old Ackley was expected to get more at-bats this week during New York's homestand against the Boston Red Sox. He is batting .212 with six home runs and 19 RBIs this season.
Cotham, 27, was called up from Triple A Scranton/Wilkes-Barre to fill Ackley's spot on the roster. The right-handed pitcher made his MLB debut Wednesday with the Yankees, and threw 1.2 shutout innings with four strikeouts against the Texas Rangers.
- Kayla Lombardo