Liam Rosenior on Monday demanded an improvement in discipline from his Chelsea players after Pedro Neto became their ninth player to be sent off this season, threatening to drop players who do not show greater control.
Sunday's 2-1 loss to Premier League leaders Arsenal at the Emirates Stadium means Chelsea have won just two of their past six matches in all competitions.
They are sixth in the Premier League table ahead of Wednesday's match at fourth-placed Aston Villa, three points behind Liverpool in the battle for Champions League football next season.
Ill-discipline has been costly for Chelsea this season, with Neto the seventh Stamford Bridge player to be shown a red card in the Premier League.
Chelsea boss Rosenior, who replaced Enzo Maresca in the hot seat in January, said Neto had apologised to his teammates after he was dismissed in the 70th minute.
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"My job is to create a culture of accountability, where if you make a mistake, it's OK, you hold your hands up and you make sure it doesn't happen again," said the English manager.
"But you have to hold your hands up to the original mistake. If I make the wrong team selection, or I get something wrong, my job is to be accountable, and it's the same for my players in that moment."
Rosenior said Portugal winger Pedro, who will miss this week's match at Villa Park, had apologised to his teammates.
"I just need to see an improvement in the behaviour now," he said.
"And it's not just Pedro. We've had bookings. People speak about dissent. We've had needless bookings in terms of fouls. If we are to improve and get to where we want to be, we have to make a conscious step now to make sure it doesn't happen again."
The Chelsea boss said there were different approaches to tackling the issue.
"Sometimes it's not a stick, it's showing what the value of not having a red card is," he said. "If you look at our stats, when we have 11 men on the pitch, before my job here and after my job here, our percentage chance of winning goes through the roof.
"So that needs to be motivation in itself, to make sure we stay disciplined in key moments, reacting to setbacks. Sometimes a setback is giving the ball away, sometimes a setback is a referee making a decision you disagree with.
"In that moment, you have to react positively and you have to think of the next thing. Those are the things we have to go after in order for our discipline to improve."
Rosenior added, "You pick players who are showing that improvement. I can't afford to go through a season every two games or every three games with a red card; it's just not possible.
"So I need to see improvement in that, and I need to adjust my team selection based on who's showing those capabilities."