Gary Rowett hit out at Ashley Fletcher's "blatant foul" that set Middlesbrough en route to a 2-0 Championship win at Millwall.
Fletcher clipped Lions defender Jake Cooper's heels, ghosted through acres of space and fed Britt Assombalonga for the opening goal that turned Wednesday's gritty clash at The Den.
Fletcher then converted a late penalty he had won himself, when being upended by the luckless Cooper.
Neil Warnock's Boro saw their relegation dogfight boosted by the win, while Rowett admitted Millwall's play-off battle is now on the line.
"What looked like a trip, what felt like a trip, was a trip," said Rowett.
"In a tight game, very physical, very direct, it always felt as though one moment would decide the game.
"I'm not going to excuse our performance, because it wasn't good enough, but it was a blatant trip.
"He didn't mean to do it, by the way, it wasn't intentional. But he's caught his feet, that's kicked his other leg and he's fallen over, Jake Cooper.
"What's very disappointing is the linesman who is two yards away, and the referee between them – you have to make what looks very much like an obvious decision, because it's so controversial. If you get it wrong, it changes the game.
"And unfortunately today the referee and the linesman got it horribly wrong between them.
"It happens in games, he's clipped his heels. But the fact he's clipped his heels, he's fallen over and it then becomes a two-versus-one, it's obvious.
"I think I could have given that with my eyes closed. I've watched it about five times, it's a blatant foul.
"They've got a big one wrong, and it's cost us the game. I can only be disappointed with that. Those moments open the game up.
"And then their second goal comes from us trying to chase the game and get back into it. We're still in the mix for the play-offs but we're running out of games.
"And if we play like that we won't get there anyway. There are some big games still to come. We go to Hull, and the simple fact is we've got to go there and put in a much better performance."
New Boro boss Warnock has now claimed two wins in four matches at the helm, and believes his new charges must keep mentally strong to avoid the drop.
When quizzed on whether Fletcher fouled Cooper in the build-up to the first goal, Warnock could only reply: "Listen, I'm doing an Arsene Wenger, I haven't seen it!"
But he then praised his side's battling victory, continuing: "I had a chat with the players afterwards on the pitch, you have to look at yourselves sometimes in the mirror.
"It's not all about managers, you've got to want to be a winner, it doesn't just come to you.
"Djed (Spence) had broken his nose in the first half and he was a bit worried about his good looks I think at half-time.
"And I said to him, 'the only answer to that Djed is to win the game, win the game and know you'll come off the pitch having played your part'."
Neither set of players took a knee before kick-off, with Rowett relaxed about that move.
"I think it was something all the EFL teams wanted to do in the first games and then after I think they have to do it in the Sky games," said Rowett.
"But I don't think it's something people have to do every single game. The stance was made and I don't think it's something people have to do every single game."
