McDonald struck a 2-1 winner for the Hoops in injury time five minutes after Chris Killen had cancelled out Fabian Yantorno's first-half free-kick for Gretna.

The Australian, whose late double for Motherwell prevented Celtic winning the Scottish Premier League at Fir Park in 2005, was delighted to follow up his last-gasp winner against AC Milan on Wednesday with another strike that will endear him to the Hoops support.

"This ground holds special memories for me," McDonald told BBC Radio Scotland.

"I love it here and I was thinking halfway through this wasn't going to be a happy return for me.

"But I'm delighted to get the goal again in the 90th minute. We're making some nice habits of that but hopefully we don't have to do that every game."

McDonald revealed there was "true belief" they could win the game and return to the top of the SPL after Killen's first Celtic goal.

"They were in our faces, there were always two or three people around the ball every time you got it," he added.

"Full credit to them, but I guess the game is not over until it's over.

"Five minutes is a long time in football. Everyone was saying 'we are going to go on and win this'.

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Yantorno struggled to take in the fact Gretna had lost their first meeting with Celtic after leading for so long.

"I think we had a great game," he said.

"Unfortunately the last five minutes were unbelievable.

"It's great for me to score against this team. They won on Wednesday against the best team in Europe.

"We have to keep working hard. If we play like this, we are going to win more games."

Celtic boss Gordon Strachan felt his side were guilty of over-elaborating in the first half.

"We didn't play reality football," he said.

"There was a bumpy pitch and the ball seemed out of shape.

"They were right up for it. I thought it was going to be one of those days but thankfully the boys didn't see that coming and they kept driving on."