Williamson has scored once for Preston since arriving on loan from Watford
Preston boss Alan Irvine has questioned the Football Association's decision to uphold Lee Williamson's red card against Birmingham City at the weekend.
The 26-year-old will miss North End's final home game against QPR on Sunday after being given a three-match ban for a clash with Lee Bowyer.
"It's a decision which has surprised and disappointed me," Irvine told BBC Radio Lancashire.
"I've not been given any idea why it was rejected at this point."
Irvine admitted he gathered opinions from a number of sources, including key members of the Professional Game Match Officials Limited.
He is absolutely devastated that the decision has gone against him
Preston manager Alan Irvine
"We're asking for an explanation, which I think we're entitled to," he added.
"Everyone I've spoken to in football believes that Lee was not guilty of violent conduct, that includes Keith Hackett and David Allison from the PGMOL.
"I consulted these people before making the appeal because I didn't want to waste anybody's time.
"They believed and I believe that we had a very strong case," said Irvine.
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