From Will Carroll at Baseball Prospectus (subscription):
The concern remains that the stamina and crepitus in Hafner's shoulder won't allow him to play all season without problems like this. The natural solution will be a strengthening-and-conditioning program. The Indians' training staff is one of the best in the game, so if anyone can keep him healthy, it's them, especially with their intimate knowledge of the situation. Hafner is likely to miss a bit more than just the minimum, but he should be back to level quickly thereafter.