The Oakland Athletics will be without closer Trevor Rosenthal to start the season after he was placed on the 10-day injured list Thursday with a shoulder injury.

The Athletics also announced that right-hander Mike Fiers had been placed on the 10-day IL.

Rosenthal joined the Athletics this offseason on a one-year, $11 million contract, with sources telling ESPN's Jeff Passan at the time that the right-hander chose the higher annual salary and save opportunities over other multiyear options.