Harrison broke his nose in Saturday's 2-2 draw with Gillingham in League One, but was determined to play against Huddersfield Town on Tuesday. As it happened, Harrison missed that game, and will shortly be going under the knife to have an operation to fix the problem.
Another key player out on Saturday will be central defender Ian Sharps, who has been missing for some time.
However, he good news is Sharps will be returning to full training new week, hopefully in time for the Friday night match against Scunthorpe.