Midfielder Reilly scored his first goal for Birmingham to put them ahead in Saturday's 1-1 draw at Huddersfield but was forced off at half-time having struggled with illness in the build-up to the fixture.
Spector replaced the teenager at half-time but has suffered a recurrence of the ankle injury which had ruled him out previously.
Marlon King, Nikola Zigic and Peter Lovenkrands joined Spector in having returned from injury and suspension to make the bench against Town at the weekend, and the attacking trio will be in contention once again.
But on-loan winger Robert Hall has been denied permission to play by parent club West Ham. while Akwasi Asante, Papa Bouba Diop, Darren Ambrose, Hayden Mullins, David Murphy, Stephen Carr and Will Packwood all continue to be ruled out through injury.
Blues and Leeds drew 1-1 in the initial meeting at Elland Road, with a home tie against Tottenham awaiting the winners in the fourth round.
- Sports & Recreation
- Peter Lovenkrands