Liam Rosenior has been far from impressed with the level of discipline in his Chelsea squad.
Chelsea lost 2-1 to Arsenal on Sunday, with Pedro Neto picking up two bookings in the space of three second-half minutes.
Neto was booked for dissent before he then lunged in on Gabriel Martinelli.
Chelsea have now received nine red cards in all competitions this season.
Only Sunderland in 2009-10 (eight) and Leicester City in 1994-95 (eight) have had more different players receive a red card in a Premier League season than Chelsea this term (seven).
And Rosenior was blunt in his assessment of Chelsea's behaviour.
"It needs to improve promptly," he said while looking ahead to Wednesday's clash with Aston Villa.
"My job is to create a culture of accountability, whereby if you make a mistake, you hold your hands up and make sure it doesn't happen again. But you have to hold your hands up to the original mistake though.
"Pedro [Neto] has apologised to the group. We will miss him for the next game. I need to see an improvement in the behaviour now.
"It's not just him though, we've had bookings for needless dissent and fouls. If we're 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."
Rosenior was specifically asked about vice-captain Enzo Fernandez, who has picked up 10 bookings this season.
"He is a top leader," Rosenior said of the Argentine.
"There's something that needs to improve there. We're a young team, it's not an excuse but we are one of the youngest in the league and in Europe.
"The beauty of having a young team is sometimes you need to go through experiences to improve, it's a massive learning experience. We have to learn from these setbacks we're having."
5 - Five of Chelsea's last six defeats in all competitions have come against teams beginning with the letter A:
— OptaJoe (@OptaJoe) March 2, 2026
Atalanta
Aston Villa
Fulham
Arsenal
Arsenal
Arsenal
Alphabetical. pic.twitter.com/T2OV5Gxvoz
PLAYERS TO WATCH
Aston Villa - Ollie Watkins
Watkins has scored four goals in his last six Premier League games against Chelsea, though all have come at Stamford Bridge.
He netted both goals in their 2-1 win in the reverse fixture in December, with Anwar El-Ghazi the last Villa player to score home and away against the Blues in a league season (2020-21).
Chelsea - Joao Pedro
Joao Pedro has been directly involved in five goals in five Premier League appearances against Villa (two goals, three assists) – against no side has he been involved in more in the competition.