Axford (shoulder) will undergo an MRI on Wednesday, Jane Lee of MLB.com reports.
Axford was placed on the 10-day disabled list Wednesday, though it can be backdated a few days because he didn't appear in either of the Athletics' first two games. He apparently felt shoulder discomfort while warming up Tuesday. Manager Bob Melvin is hopeful the 34-year-old can return next week, though more should be known after his test results are revealed.