Roberto di Matteo says Chelsea must tighten up defensively after seeing his side revitalise their Champions League title defence with a last-ditch 3-2 win at home to Shakhtar Donetsk.
The hosts were seconds from an unhelpful draw that would have left them in third place in group E, when substitute Victor Moses met Juan Mata's injury-time corner with a header that found the top-right corner.
They now lead Shakhtar by virtue of a better head-to-head record and are a point clear of Juventus, who play host to Chelsea on November 20 in a game that could decide whether or not the champions progress to the last 16.
Di Matteo admitted that the manner of the victory had carried "an element of luck", and he castigated his players for twice letting the lead slip from their grasp. "We need to work on closing out games," said the Italian, who has seen his team ship 14 goals in their last six games.
"You look at the goals. It's not like we were outnumbered, but we certainly need to work on the automatisms of our defensive organisation. But it will certainly improve over time."
Prior to Moses' last-gasp intervention, Chelsea had managed to remain in the game despite being outplayed by Shakhtar for long periods, just as they had been in the 2-1 loss to the Ukrainian champions at the Donbass Arena.
"We didn't have Frank Lampard available, Ashley Cole wasn't available, and JT [John Terry] didn't play," Di Matteo said. "There's a lot of Champions League experience that wasn't on the pitch and under normal circumstances, you'd want them to be there. But I thought the players who did play did well under enormous pressure, and they deserved credit for that. We managed to win the game under a lot of pressure."