Chris Carter was removed from his game with Triple-A Sacramento without injury in the fourth inning on Sunday.
It's not hard to put two and two together, here. Daric Barton left Sunday's game with left shoulder spasms. If Oakland needs a replacement for any length of time, the slugging prospect Carter would likely be that guy. Carter was recently moved to the outfield to give him more options for future playing time, but he is a natural first baseman. He's crushing the ball at Triple-A and may be within a few hours of a promotion.
Source: Susan Slusser on Twitter