Wagner is dealing with an oblique strain and hasn't done any baseball activity since the beginning of March, Kevin Acee of the San Diego Union-Tribune reports.
Per Acee, Wagner will "almost certainly" start the season on the injured list. The infielder had been slated to battle for a reserve role during spring training, but he got into only five games before getting hurt, going 0-for-9 with two walks and two strikeouts. Even if Wagner was healthy, his likelihood of making the Opening Day roster had been considered slim.