Chelsea manager Jose Mourinho has called for an immediate response from his players against Schalke in the Champions League on Wednesday following their unscheduled defeat at Newcastle United.
The Europa League champions appeared to be gathering momentum after winning all six of their matches in all competitions in October, only to slump to a 2-0 loss at St James' Park in the Premier League on Saturday.
On Wednesday they will be bidding to repair their home record in European competition, having seen a 29-game unbeaten run in the Champions League group phase ended by Basel in their opening Group E fixture.
Their subsequent victories away to Steaua Bucharest (4-0) and Schalke (3-0) took them to the top of the pool, but another setback at Stamford Bridge would compromise their chances of reaching the last 16.
"We are in a stable position to qualify in the Champions League, but if we lose again we are in a difficult position," Mourinho told the Chelsea website. "So Wednesday is an important game for us."
Mourinho has vowed to shake up his starting XI, having been critical of his players' application after the defeat at Newcastle.
Andre Schurrle, Willian and Samuel Eto'o will all hope to start after coming on from the bench against Alan Pardew's side, while Juan Mata's place once again looks at risk after he was hooked in the 62nd minute.
"I will make changes. Not 11 changes because that would be too much, but changes for sure," said Mourinho.
"I don't know my best team because we have this kind of performance (against Newcastle).
"I know basically which is my best team, but it depends on the way we perform because performances and results push you for decisions."
Mourinho can at least console himself that, with the exception of long-term knee injury victim Marco van Ginkel, he has a full complement of players to choose from.
The same cannot be said of his Schalke counterpart Jens Keller, whose injury-ravaged squad have been unable to keep pace in the Bundesliga this season.
Schalke won 2-0 away to Hertha Berlin on Saturday, but they are languishing in sixth place -- 12 points behind leaders Bayern Munich -- after losing four of their opening 11 games.
The Gelsenkirchen club have been hit by injuries to Marco Hoger, Jefferson Farfan, Chinedu Obasi and Klaas-Jan Huntelaar, although Greek centre-back Kyriakos Papadopoulos is close to a return from a knee problem after playing for Schalke's reserves last weekend.
One positive by-product of the injury blight has been the emergence of youngsters such as 18-year-old attacking midfielder Max Meyer, who last month became the youngest player to score in three consecutive Bundesliga games.
However, captain Benedikt Howedes has admitted: "We cannot compete against top teams like Chelsea at the moment."
Schalke's last visit to England came almost exactly a year ago, when they won 2-0 against current Premier League leaders Arsenal en route to topping their group.
Chelsea have not lost at home to a German team in six previous encounters, but Schalke may take heart from the London club's curious habit of struggling for form in November.
Chelsea have won just six out of 21 games that they have played in the last three Novembers, and former manager Roberto Di Matteo paid with his job this time last year after the defending champions fell in the group phase.
Goalkeeper Petr Cech says that his side are aware of the quirk and determined not to succumb to their November hoodoo again.
"We always say, 'Be careful, because November was not the greatest month,' and we said it again two years ago and again last year," said the Czech Republic international.
"The last three seasons it didn't really work out and that is very hard to explain.
"But we are now in a good position in the league and a good position in the Champions League group, and we have to carry on like that because it's a long campaign."