Robert Hall was poised for his first Birmingham start before a bout of sickness ruled him out of Tuesday night's 1-1 draw at Blackpool.
On-loan West Ham youngster Hall impressed with a lively cameo during Saturday's 3-2 defeat to Derby and was set to be rewarded by boss Lee Clark.
But Clark revealed the 19-year-old fell ill in the team hotel on Tuesday afternoon when he was briefing the Blues squad for the match.
"When we were in the hotel talking about the game, watching footage and talking through the tactics, Robert Hall became ill in the meeting," he said. "We had to stop the meeting halfway through when he was ill, sent him to bed and tried to get a bit of food into him. That didn't work, it didn't stay down.
"His 35 minutes on Saturday were excellent. He was going to start, in that system he would have been excellent for us with his pace, his directness and his penetration.
"Unfortunately it wasn't to be and he's a big doubt for Friday now because the doc seems to think this isn't just going to be a 24-hour thing. This is the first time someone's vomited during my team talks so that's a new one!"