Roberto Di Matteo says Chelsea must tighten up defensively after seeing his side revitalise their UEFA 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 20 November in a game that could decide whether or not the champions progress to the last 16.
Di Matteo admitted that the manner of Wednesday's victory had carried "an element of luck," and he castigated his players for twice letting the lead slip from their grasp.
"The fact we couldn't hold onto the lead twice worked against us. 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. We've got a lot of players back, so 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.
The largesse of visiting goalkeeper Andriy Pyatov played a part.
The Shakhtar number 30 first saw Fernando Torres charge down his kick to put Chelsea ahead in the sixth minute and was then lobbed by Oscar after a weak clearing header shortly before half-time.
Shakhtar's Brazilian playmaker Willian equalised on both occasions with almost identical goals, meeting right-wing cut-backs with side-footed shots to leave Petr Cech wrong-footed.
Blues miss experienced campaigners
In the absence of the injured Ashley Cole, Chelsea repeatedly found themselves exposed on their left flank, and with John Terry not match fit after his four-match domestic ban for racially abusing Queens Park Rangers' Anton Ferdinand, Di Matteo conceded that his side lacked a bit of know-how.
"We didn't have Frank Lampard available, Ashley Cole wasn't available, and JT (Terry) didn't play," he 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. I thought we deserved to win because we did a lot of good things. We put them under pressure, especially in the first half, and that's how we scored the two goals."
Moses' late cameo meant that Shakhtar left London with the taste of defeat in their mouths for the first time this season.
Lucescu bemoans defensive errors
Although they can move to within touching distance of the last 16 if they win at Danish competition debutants FC Nordsjaelland in 13 days' time, coach Mircea Lucescu said he was "disgusted" by the way his side lost their unbeaten record.
"We gave them the possibility to have a corner and it's painful to lose such a match," said the Romanian. "But we have another two matches to play and Chelsea are on the same number of points."
Chelsea's ongoing participation in the tournament will be on the line when they visit Turin in two weeks, and Di Matteo knows his side cannot afford to lose.
"We need some points out of the last two games," he said. "We need to win the last game (at home to Nordsjaelland), certainly, and we need a point in Turin as well."