Mauricio Pochettino appeared to suggest that Chelsea lacked heart in their 2-2 draw with 10-man Burnley.
The home fans again showed their discontent, with many booing at the final whistle at Stamford Bridge.
After Lorenz Assignon had been sent off, Cole Palmer scored from the penalty spot and later restored the lead after Josh Cullen’s equaliser, but Dara O’Shea levelled again.
Blues boss Pochettino said: “We’re disappointed and frustrated with the way we managed the second half.
“We are a team that, when we have possession and go forward, we are capable of creating chances.
“But we didn’t show the energy and anger to compete in the Premier League. In the defensive phase we conceded too much.
“That is why I am so upset and disappointed. It’s more here (pointing to his heart) and it’s more here (pointing to his head) than in your legs. It’s more about being strong as a group and strong like a team.
“For different reasons we are so slow evolving in this area and that I think is the key today.
“Did we have energy when we have the ball and go forward? Yes. But when we don’t have the ball we don’t show the same energy.
“Today, sorry, but I am not happy with the performance when we don’t have the ball. We need to have the capacity to go and win the ball back.”
A win would have taken Chelsea up a place in the Premier League table, but they remain 11th.
“It’s difficult to accept not winning, because for me it was a must-win game,” Pochettino admitted.