Dundee United manager Peter Houston refused to criticise referee Brian Winter for his apparent mistake in failing to send off St Johnstone substitute Steven Anderson in his side's 1-0 home win.
United's victory over their derby rivals - courtesy of David Goodwillie's 61st-minute goal - ended in controversy when Anderson appeared to be booked for the second time in the match, but Winter did not brandish a red card and the Saints defender remained on the pitch for the closing stages.
Houston felt it was a genuine error, saying: "If it is a mistake from Brian, then it will be an honest mistake.
"I did not know at the time that Anderson was due to be sent off as there was a spate of bookings and I was concentrating on which of my players had been shown a yellow card.
"There was an incident where five players were booked at once and I believe now that Steven was the first player to be shown a yellow.
"Brian might have made a mistake by not making a note of that but these things happen. I hope he is dealt with leniently because he's an honest guy and we all make mistakes."