Edward Mujica suffered a fractured right thumb in Thursday's loss to the Rays and will head to the disabled list.
Athletics acquired RHP Edward Mujica from the Red Sox for a player to be named later or cash considerations.
Red Sox designated RHP Edward Mujica for assignment.
Red Sox manager John Farrell confirmed Sunday that Edward Mujica would begin the season as his team's closer with Koji Uehara sidelined.
Edward Mujica allowed a run and two hits in his inning of relief Thursday against the Twins.
FOX Sports' Ken Rosenthal reports that the Red Sox "have expressed a willingness" to trade Edward Mujica.
Edward Mujica worked a scoreless ninth Sunday to earn the save against the Orioles.
Edward Mujica converted his seventh save of the season on Friday, working a scoreless 10th inning to preserve a two-run advantage over the Orioles.
Edward Mujica secured his sixth save of the season with a scoreless inning against the Royals on Friday.
Edward Mujica retired all three batters he faced in the ninth inning, earning his fifth save in Thursday's win against the Royals.
Edward Mujica earned his fourth save of the season Saturday as the Red Sox topped the Blue Jays 4-3.
Edward Mujica will fill in as the Red Sox's closer while Koji Uehara gets at least the next couple of days off.
Edward Mujica nailed down his third save of the season in Wednesday's win over the Reds.
Edward Mujica earned his second save of the season with a perfect ninth inning against the Twins on Tuesday.