Cesar Azpilicueta said Chelsea lost their grip and control in the FA Cup win at Hull City, claiming players were too eager to put themselves before the team's best interests.
The Spaniard played the full 90 minutes against the Championship side, as Chelsea battled out a 2-1 victory on their travels.
Chelsea were dominant for the first 70 minutes and should have added to goals from Michy Batshuayi and Fikayo Tomori, but they allowed Hull too much of the ball after that point and almost paid the price.
A fortunate reply from Kamil Grosicki, whose free-kick took a big deflection off Mateo Kovacic to wrong-foot Willy Caballero, saw the Tigers claw their way back into the match with 12 minutes remaining.
Hull had chances to force a replay too, with Chelsea forced into some desperate and often untidy defending to remain ahead.
"With the chances we had, we cannot concede in these kind of circumstances and we have to control better," Chelsea captain Azpilicueta said.
"We know we have to improve our game if we want to improve as a team and go far, because tonight was a night we could have handled much better.
"It's not the first game where we didn't manage the game well, and at the end there we were on our box suffering. Sometimes we can be punished but tonight not, but we know we have to improve."
Speaking on BT Sport, Azpilicueta added: "For moments we stopped playing as a team and we started doing individual actions that is not our game and we got punished.
"And if we want to play against the best teams and to fight for trophies, we have to improve."
The absence of top scorer Tammy Abraham, who has an ankle injury, meant Chelsea were reliant on the likes of Batshuayi and Pedro – the latter could have scored at least twice but failed to convert chances.
Goalscorer Tomori, who headed in a free-kick from Ross Barkley to put Chelsea 2-0 up after 64 minutes, said Frank Lampard's men would have been able to cruise home if they were able to finish the openings they carved out when on top.
"In the first half we probably could have killed the game, but we didn't take our chances," Tomori said.
"We said at half-time that because we hadn't taken our chances we had to be solid at the back, try to score another one, but we need to be more clinical.
"I think my goal came at a good time, but it got a bit difficult towards the end when they scored the free-kick.
"It's a one-off game and teams want to go for it. They were never going to stop and we knew that.
"If we'd got a third goal it would have been a lot easier for us but we didn't manage to get that so we had to ride it out."