Matt Oakley was taken off in Tuesday's 0-0 draw with Gillingham after suffering a dislocated shoulder which is set to rule him out for the rest of the npower League Two campaign.
And the former Southampton man joins Tommy Doherty, Liam Sercombe and Alan Gow on the sidelines.
Sercombe is targeting a pre-season comeback after a broken ankle, Gow could return should the Grecians make the play-offs but Doherty discovered this week that his back injury will sideline him for at least four weeks - leaving their manager light in the middle of the park.
"It is really strange how it goes," Tisdale told Press Association Sport. "But we just have to get on with it and we'll have to adapt and prioritise other areas of the pitch."
Mark Molesley returned from suspension against the Gills while Jimmy Keohane stepped off the bench when Oakley went to hospital and the duo are likely to start against the Bantams.