Scott Parker was left disappointed and angry after Ademola Lookman's spot-kick shocker cost Fulham a point at West Ham.
Lookman astonishingly chose the last kick of a match where his team were losing 1-0 to attempt a Panenka-style penalty.
The effort was so awful that West Ham goalkeeper Lukasz Fabianski, who had begun to dive to his right, actually had time to get back up and make the save.
It was a contender for worst Premier League penalty ever, and Lookman looked devastated as he left the pitch.
West Ham had only taken the lead in the first minute of stoppage time through Tomas Soucek but thanks to Lookman's calamity it proved to be the winner.
Parker said: "I think at the moment it's so raw, my emotions are one of disappointment, anger a little bit.
"When you are young, you make mistakes and that's where Ade is. You can miss a penalty but when you take one like that you have to hit the back of the net.
"Ade has been fantastic since he's been here. He needs to learn from what happened tonight.
"He's made a mistake, not because he's missed a penalty but because he's taken one like that. And at that point in the game. He's put himself on show.
"He'll bounce back. He's an unbelievable character who's made a bit of a mistake."
Lookman took to Twitter on Sunday and vowed to make up for his error.
He tweeted: "After yesterdays mistake, I take full responsibility and onus for it.
"To my team-mates, manager and the supporters I vow to put the next one in. I will not let one failure hold me back."
After yesterdays mistake, I take full responsibility and onus for it. To my teammates, manager and the supporters I vow to put the next one in. I will not let one failure hold me back. @FulhamFC pic.twitter.com/LpI0Z3pqk8— Ademola Lookman (@Alookman_) November 8, 2020
After a forgettable 90 minutes the match burst into life in stoppage time when West Ham's £25 million new boy Said Benrahma teed up Soucek to slot home.
Parker complained that Sebastien Haller was offside in the build-up - "It's baffling to me," he said - but VAR thought otherwise.
Benrahma had an impact at both ends, tripping Tom Cairney to gift Fulham the chance to take a point only for Lookman to blow it.
Hammers boss David Moyes admitted: "If I was Scott I'd be disappointed with the goal because Seb runs offside. I think the whole offside rule with the delaying of the flag is a terrible rule.
"Said's a really good player, We're bringing him on. He had an impact in both boxes unfortunately, but fortunately it went well for us.
"It says a lot about the players. It's a change for us. We're trying not to be flaky, and if we have to win a little bit ugly, so be it. I hope we keep winning like this."