Wood has been sent back to Oakland to have his left shoulder evaluated, Martin Gallegos of MLB.com reports.
Wood was dealing with shoulder soreness during his start in Sunday's 8-4 loss to the Mariners, and the injury seems to be one that's been a problem for him for a while. A stint on the injured list would appear to be a distinct possibility for Wood, but the team is unlikely to make a decision on his status until his evaluation is completed. If Wood isn't able to take the hill for his next turn through the rotation this weekend in Kansas City, the Athletics would likely turn to Kyle Muller or Mitch Spence to start in his place.