Mason left during the second period of Sunday's game against the Capitals with an undisclosed injury, Frank Seravalli of the Philadelphia Daily News reports. Mason's injury could be serious, as he needed a lot of help to get to the dressing room. The injury came at an especially bad time for the Flyers, as his potential replacement, Rob Zepp, was injured in an AHL game Saturday night and could miss extended time. Mason's status is unclear at this point, but the team should provide an update at some point in the near future.