Chelsea manager Frank Lampard has admitted that he is considering dropping players ahead of Aston Villa's visit to Stamford Bridge on Monday.
Mikel Arteta's struggling Arsenal were the latest team to defeat Chelsea after earning a deserved 3-1 win at the Emirates on Boxing Day, the third defeat in four games for the Blues.
Lampard was left frustrated and was critical of his players who performed particularly poorly in the first half. Now, having hammered his players for "not following the basics," Lampard has admitted there will be consequences after a bad run.
"The first half certainly was our worst performance of the season as far as I saw it," Lampard told reporters ahead of his side's clash with Villa. "We lacked energy. We are in a position in the last four games of losing three and only winning one. So that needs a reaction.
"They did [lack character] and the players know that. The first half we lacked it. Second half we didn't, to be fair, and there will be some players that come out of it with credit for the performances in the second half. But today we did.
"I’m not going to generalise that that’s the case because it’s not. But today we did and football will punish you if you turn up and have that sort of lack of the basics in your game.
"There will be some changes and I knew that anyway. I am certainly not going to bang the drum about the quick turnaround after our performance today. That's not to point. We are playing two games in two days and [changes] would have happened anyway.
"Some of those will happen because of how the game went and people will have to come in and inject energy and personality."
Chelsea must count the cost of their efforts in the London derby ahead of the match against Dean Smith's side, who are one of seven teams above them in the Premier League after 15 games.
Ahead of the match, Lampard confirmed that Hakim Ziyech remains out injured but hinted that Callum Hudson-Odoi would start. The 20-year-old was one of the few bright performers off the bench against the Gunners after coming on at half-time for an out-of-form Timo Werner.
"Some people wanted to talk us up as title contenders but I never accepted that because we are not there," he added. "That takes time to build and days like today are ones where we have to learn big lessons from.
"You learn about the players and the players have to learn about themselves. Some of them are young and some of them are new to the Premier League and these tough times are things that we will have to go through.
"I don’t think this season was ever going to be plain sailing, winning every week. We got confident and we got into a position where we were not losing games and winning a lot of games.
"When you lose a couple of games, things become a lot tougher and the only way out of it is the fight and work hard. That’s what I will be instilling in the players – that idea – because it’s the only way that you get out of what is a difficult little period for us."
Chelsea next face an in-form Villa before Manchester City visit after the New Year.
Lampard spoke about his respect for the Midlands side and the impact that fellow legendary Blues player John Terry has had as Villa's assistant manager.
"I’m sure John has an influence because he’s one of the greatest centre-backs that played in the Premier League for England and in the world for a long time and an absolute wealth of knowledge," he added.
"His input will be invaluable to Dean Smith and all the staff and the team are working hard. You’ve seen a big uplift and I’m sure there’s a lot of hard work behind the scenes from John and all the staff.
"I think they are a good team with very good individual players. They added to their squad in a very good way in the off-season. Good manager, good coaches and good players that are playing well and they are in a really good time at the moment.
"I’m not completely surprised. It will be a tough match."