Aberdeen goalkeeper Joe Lewis apologised to his teammates in the dressing room after his late mistake handed St Mirren a 2-1 win and a place in the quarter-finals of the Betfred Cup.
Lewis attempted to pat down Jamie McGrath's 88th-minute shot from 22 yards but saw the ball slip calamitously through his legs and he was unable to claw it off the line.
The Dons had levelled in the 42nd minute through Niall McGinn, who took advantage of a fortunate deflection sending the ball into his path, to cancel out Ilkay Durmus' early free-kick.
They had no time to respond after Lewis' error, but manager Derek McInnes refused to scapegoat the goalkeeper.
He said: "Joe came into the dressing room and apologised. It's a lonely place for a goalkeeper because there is no hiding place.
"Anybody who has watched us consistently over the years since Joe signed will know that he's saved us more than he's cost us.
"It's uncharacteristic and it cost us today but I'm not going to hang him out to dry for us losing the game."
St Mirren were good value for their win, though, and boss Jim Goodwin praised his side's resilience.
He said: "I was really disappointed to be level at the break considering how much we dominated in the opening 45 minutes. If we had been 3-0 up then there couldn't have been many complaints.
"When they equalise, it would have been really easy for the team to capitulate, so credit to the boys because they didn't allow that to happen.
"I asked them to replicate their performance at half-time as I believed that would be enough to win the game and, thankfully, that proved to be the case."
The victory means St Mirren are now unbeaten in their last seven games. The Buddies' season has been disrupted by games being cancelled due to coronavirus restrictions, but Goodwin is confident in his side's ability.
He added: "There's been great belief in our group. We know why our poor run happened, because we've got genuine reasons as to why our form dipped. We started the league well, then we had Covid – it took its toll but we are past that now.
"We've got a fantastic group when everyone is healthy. I've always said that, outside the top four teams in the league, we are all capable of beating each other.
"It's about consistency, momentum and confidence, so hopefully we can take that into next weekend's game against Aberdeen. They'll come down here hurting, like wounded animals and wanting revenge."
