St Johnstone manager Tommy Wright will consider lodging an appeal against the red card shown to Dave Mackay in Wednesday's 3-0 defeat by Celtic.
Mackay was dismissed after Derk Boerrigter went down, then Nir Biton converted the spot-kick to give Celtic a two-goal lead.
The Saints captain had earlier been denied a penalty following Virgil van Dijk's challenge.
"One was a penalty and one wasn't," declared Wright.
"Van Dijk leaves his leg out. There was contact. It is the wrong decision.
"If there was contact [with Boerrigter] it was minimal and it didn't make him go down because he didn't go down in the contact; that is clear for everyone to see.
"And he actually collapses his right leg which is the leg furthest away from Dave Mackay, if he did make contact.
"It's not my view that counts, it is the referee's that counts. There is enough grounds for appeal and I have spoken to [referee] John [Beaton]."