Spencer saw red for violent conduct during last weekend's 3-1 win at Shrewsbury and now begins a three-match ban.
Striker Phil Jevons is rated doubtful to face the Gulls as he battles to shake off a hamstring strain.
Defender Paul Scott remains sidelined after a knee operation, but defender Will Haining should come back into contention after recovering from injury.
McIlroy has revealed he almost quit the club after his side's 3-1 defeat at Torquay earlier in the season.
He said: "Everything seemed to go against us and after we ended the game with nine men I was at a real low. I seriously thought about calling it a day."
Source: PA
Source: PA