Frank Lampard said Chelsea's comeback victory against Arsenal on Sunday was down to "spirit and desire" after admitting his team were "awful" at the start of the Premier League game at the Emirates Stadium.
Chelsea scored two late goals, the first courtesy of a Jorginho tap-in after Arsenal goalkeeper Bernd Leno misread a wide free-kick from Mason Mount, before Tammy Abraham slotted home the winner. Pierre-Emerick Aubameyang had opened the scoring in the 13th minute during a spell Arsenal utterly dominated.
Setting his team up in a 3-4-3 formation, similar to the structure that outclassed Tottenham Hotspur at the Tottenham Stadium a week ago, Frank Lampard made a vital tactical change after 34 minutes, swapping left wing-back Emerson Palmieri for midfielder Jorginho as Chelsea regrouped in a 4-2-3-1.
The change paid dividends as Chelsea controlled much of the remainder of the match, even if they had to wait until the 83rd minute to pull level.
"We were so awful for 30 minutes, slow lethargic, nervous," Lampard told the BBC. "The opposite of against Tottenham. We gave Arsenal everything they wanted. We made the change early, I felt it had to be done and the second half we dominated.
"After 10 minutes or so, it was clear that Arsenal had seen us play against Tottenham and made us into a back five instead of a back three. They were on top and there was a lack of balance to our team. The sub gave us another man in midfield and gave us more urgency."
Lampard suggested that a few words were said during half-time to motivate his players, and whatever was said evidently worked. It was another valuable three points for Chelsea in their pursuit of a place in the Premier League's top-four, having hit a troublesome run of form that has included five defeats in their past seven matches. Another loss would have seen fifth-placed Manchester United trail by just one point.
"From my point of view you can accept a miss-pass, but you can't accept lethargy in a London derby. The players were told that and they delivered," Lampard said. "The second half was nothing to do with tactics - it was all to do with spirit and desire.
"I still haven't bounced back from Boxing Day mentally [and the 2-0 loss to Southampton]. Our next home games, we will do everything we can to turn the corner. We're still in fourth and want more and the home games have been different so we have to focus on them when they come around."
For Mikel Arteta, his first win since taking over as Arsenal manager now stretches to three games following away draws to Bournemouth and Everton.
However, he could count himself somewhat unfortunate, considering Chelsea's first goalscorer was perhaps lucky to still be on the pitch having escaped a second yellow card when he tugged back Matteo Guendouzi, while he could not legislate for Leno's error.
"It was very cruel the way we lost it, in the first half we saw a lot of positives and saw what we are trying to implement. But the way we conceded was disappointing," Arteta said. "It was clear why it was disappointing, I don't need to say any more.
"Our reaction was right, we were doing the right things, it is hard to dominate all periods of the game against this team. We started to defend too deep and our energy levels are in a different place to Chelsea's.
"We need to sustain those periods for longer periods in the game and against top sides. Individual errors cost you games but I can't fault the effort, commitment and for putting in place what we practised."
The defeat compounds Arsenal's poor campaign, with the club languishing in 12th in the Premier League standings and next face a resurgent Manchester United at the Emirates on New Year's Day. Chelsea, meanwhile, travel to Brighton & Hove Albion on the same day.
