Jordan Hugill was substituted in the second half of Preston's draw with Birmingham due to fears over a head injury.
The North End striker was treated after going down in the second half, being replaced by Alan Browne 67 minutes into the disappointing 1-1 draw at Deepdale.
PNE boss Alex Neil explained post-match that results of concussion tests carried out by physio Matt Jackson and the pitch-side doctor meant he had to come off.
"Jordan only got taken off because he failed all his tests in terms of concussion," Neil said.
"When the physio and the doctor assessed him, he didn’t answer the questions properly.
"He’s at risk that he’s not really all there to be honest. We needed to take him off."
It restricted Neil's options as his side toiled at Deepdale on Saturday, Ben Davies having been removed at half-time with a hamstring problem.
"At half-time I was tempted to make a change but I was forced into a substitution," the Preston manager said.
"I was conscious of the fact Paul Gallagher had a sore knee.
"I was conscious of the fact I had Tom Clarke and Greg Cunningham who haven’t been back long from long lay-offs.
"Tom Barkhuizen’s not been that well and then Jordan Hugill gets a head knock.
"Although I was frustrated with some of the other players who weren’t playing well I had to hold back my substitutions because I knew I had other issues."