The Mariners announced the roster move Wednesday, one day after Paxton left Seattle's game against Oakland in the first inning after being struck on his left arm by a line drive.
Manager Scott Servais said after Tuesday's 3-2 loss that Seattle "probably got a little lucky" regarding the severity of Paxton's injury. The Mariners have not disclosed a timeline for how long they will be without the star left-hander.
Paxton, 29, is 10-5 with a 3.68 ERA in 24 starts this season. The Mariners will use veteran right-hander Felix Hernandez, who recently had been demoted to the bullpen, as Paxton's replacement in the rotation.
In a corresponding roster move also announced Wednesday, the Mariners recalled right-hander Christian Bergman from Triple-A Tacoma.