Steve Morison said Leandro Bacuna held his hands up and accepted responsibility after his reckless red card played a big hand in Cardiff City's 3-0 defeat by Bournemouth on Thursday night.
The Bluebirds fell a goal behind after Ryan Christie's deflected shot found its way into the net, however they had stood up to the challenge really well against the table-topping Cherries in the first half.
But just before James Linington blew his whistle for the end of the first half, the game flipped on its head when Bacuna scythed Philip Billing down with a dreadful challenge on half way.
Bacuna was given his marching orders and it was backs-to-the-wall stuff from the Bluebirds thereafter.
And Morison said that he thought his side were playing well up until that flashpoint, which ultimately had a huge say in the final result.
"I haven't watched it back, live I thought it was a sending off," Morison said of Bacuna's challenge.
"You let your team-mates down. He knows that, he held his hands up as soon as he went in the dressing room.
"I said to all the players before the game that we need everyone pulling in the right direction, not just against Bournemouth, against anyone.
"If you don't have everyone, it becomes incredibly tough."
He added: "It was a bad tackle, the game went away from us in that moment.
"Unfortunately, up until that moment, I thought he and everyone else was having a good game.
"But everyone only focuses on the negative side and it's affected the team, which is the most important thing."
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Another moment which drew raised eyebrows from Cardiff fans was when Isaak Davies was substituted 30 minutes after coming off the bench himself.
The 20-year-old was brought on for Mark Harris at half time but, in truth, struggled to force his way into the game. On 75 minutes, he was replaced by Rubin Colwill.
When asked about the reasoning behind Davies' substitution, Morison said candidly: "He wasn't good enough.
"I'm not sending a message. He just wasn't good enough.
"I brought him on to change the game, to help us, and he was more of a hindrance than he was a help.
"So, I made the change. It's not nice. It's not something i wanted to do, but I needed to do something to try and stem their flow and get us not defending constantly.
"It's harsh, not nice, lots of people will say I only did it because he's a young lad. Ultimately, I did it because he wasn't good enough in that moment today.
"But he has had really good moments for us so far."
Fortunately for Davies, he has a luxury Bacuna does not as he will be able to put things right when City take on West Brom this Sunday.
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