Branislav Ivanovic has said Chelsea did not show enough fight as they slumped to a 3-0 defeat to Manchester City on Sunday.
Chelsea suffered their joint heaviest loss under Jose Mourinho, with the Premier League champions losing to goals by Sergio Aguero, Vincent Kompany and Fernandinho.
Right-back Ivanovic, beaten in the air when City captain Kompany scored the crucial second on 79 minutes, accepted that Chelsea had neither battled well enough nor fashioned enough chances.
"We didn't compete with them and this was the problem for us in this game," the Serbia international told reporters.
"In some parts of the game, we controlled it and looked good -- but after that maybe our concentration went down and we let them create some problems for us.
"They scored the goals and won the game, but for us we know we have to play harder.
"They used their chances and this made the difference, but also I think we didn't create enough to win the game."
Chelsea drew 2-2 against Swansea in their opening match and are already five points behind City, but Ivanovic is adamant they can overhaul Manuel Pellegrini's early-season leaders.
But he is adamant Chelsea have to be better than they were at the Etihad Stadium and said last year's title win was now irrelevant.
"We know what we haven't done well in the first two games, but there are another 36 [to go] and we have to improve ourselves," he added.
We can be better than last year as well, and we have to show that on the pitch.
"Last year we won the title and we play with extra pressure, and we have to adapt to that. We have to forget last season and start thinking about the points this season."
Chelsea are away at West Bromwich Albion next before facing Crystal Palace at Stamford Bridge, and Ivanovic believes their fightback needs to start now.
"You have to be on the top of your game and of your opponent to prove yourself and get the points," he said. "I hope in the next couple of games that we do that."