Interim manager Calum McFarlane has admitted Chelsea's dismal disciplinary record was a key reason for their failure to qualify for Europe.
The Blues finished in 10th place in the Premier League after a 2-1 defeat at Sunderland on Sunday ended their faint hopes of securing a European berth for next season.
In the last game of McFarlane's second spell in temporary charge, Chelsea once again finished with 10 men.
French defender Wesley Fofana was sent off for a second yellow card after fouling Wilson Isidor in the 61st minute.
Fofana's dismissal was the eighth red card for Chelsea in the Premier League this season and McFarlane conceded it was a major issue throughout a turbulent campaign.
"It's definitely an issue, it's definitely a problem. I think we're by far the team that's got the most red cards in the league," he said.
"Pretty sure if you look at Arsenal, for example, who have won the league, I don't think they had one red card.
"It doesn't help having that many red cards. It's definitely something we need to look at and improve for next year."
Going into the final day of the Premier League season, Chelsea sat eighth in the table – enough to reach the UEFA Conference League – but they ended one point away from European qualification, completing a wretched season that also included an FA Cup final loss to Manchester City.
McFarlane, who first stepped in following Enzo Maresca's exit, returned as interim boss for the last six games after Liam Rosenior's sacking.
Former Real Madrid and Bayer Leverkusen manager Xabi Alonso takes over on July 1 and McFarlane is adamant the Spaniard will inherit a squad capable of far more than they achieved this term.
"I think that this group has shown when they're at their best and when we're in the right place, we're a match for anyone across Europe, they've shown that this season," he said.
"That hasn't been seen enough throughout the year, that definitely hasn't been seen enough in the second part of the season. We've got some real quality players, we've got a new manager coming in who's got a brilliant reputation in the game.
"We've still had some flashes in the last month of what this group can do. It's doing that on a more consistent basis."