Lennon's side were undone by a late goal at St Mirren Park
Danny Lennon and forward Paul McGowan felt the latter was unfairly penalised in the run up to Aberdeen's equaliser against St Mirren in the Scottish Cup.
McGowan had given the Buddies the lead in the quarter-final tie in Paisley but the Dons levelled late on.
"My big question was, the free-kick against McGowan, was it a free-kick? In my opinion it wasn't," said Lennon.
McGowan added: "I don't think it was. I made it easy for the referee by diving in. The ball was there to be won."
Rory McArdle netted Aberdeen's equaliser and the replay will take place at Pittodrie on Wednesday.
"I'm very, very disappointed with the outcome after so much in the second half and how we created a lot of good opportunities," Lennon told BBC Scotland.
"It's very, very dangerous when it's only 1-0 and their flinging everything at it and you're holding on right there at the death.
"With the clear-cut opportunities that we had, the game should've been put out of doubt.
"There's always that opportunity that they can go and nick a goal and they did get a wee bit of fortune for their goal."
McGowan agreed with his manager's assessment, saying: "We should've been two or three goals up and it's heartbreaking for the boys, we're all down in the dumps.
The only thing that's missing from us at this minute time is more of a final product
Danny Lennon
"We've just got to get on with it and hopefully we can get a result up at Pittodrie."
Lennon bemoaned the loss of another late goal this season and is urging his side to learn from the disappointment.
"We should've put the ball into the corners more," said the St Mirren manager. "That's my big message to them now; to cash in on that experience and to make sure that if you're put in that situation again that you use that to your advantage.
"The only thing that's missing from us at this minute time is more of a final product."
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