Diamond headed the third goal under pressure from Vennegoor of Hesselink
Jimmy Calderwood says referee Dougie McDonald would have awarded a penalty had Zander Diamond not scored a crucial third goal in a 4-2 win over Celtic.
The Celtic bench were left angry, believing the whistle had already gone for a foul against Aberdeen.
But the Dons manager sought clarification from McDonald.
"Asking afterwards, he said he was going to give a penalty and then the linesman said it was a perfectly good goal," Calderwood told BBC Sport.
"I thought it was a perfect goal, but then Dougie blew the whistle and I thought it must have been a foul or something and a free-kick for Celtic."
Television replays suggest that a whistle was sounded around the time the ball crossed the line.
It was disallowed. The referee pointed for a free-kick
Celtic manager Gordon Strachan
But Celtic manager Gordon Strachan insisted that the goal should not have stood after Diamond, who later also scored Aberdeen's fourth, dived to head into the net under pressure from Jan Vennegoor of Hesselink.
"We heard the whistle," said Strachan. "It was disallowed. The referee pointed for a free-kick.
"Jimmy accepted it was a disallowed goal. It was astonishing to see the Aberdeen players. They accepted it was a free-kick - and then they were celebrating.
"Unfortunately for us, somehow it materialised that the radio communication broke down for the referee to the fourth official for 10 minutes after it.
"And then we were given a kind of scrambled message after 10 minutes it started working again, so that was unfortunate.
"Everybody in the stadium thought the goal was disallowed."
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