Arsenal crashed to their heaviest ever European defeat in mid-week, a 4-0 thrashing by AC Milan that has all but extinguished the club's chances of progressing to the last eight of the Champions League.
The Gunners must now pick themselves up from that traumatic trouncing as they prepare for a tricky trip to Sunderland, exactly one week after scrambling a last-gasp 2-1 win over the Black Cats in the league.
The celebratory mood that accompanied last weekend's league win -- clinched by a farewell goal from Thierry Henry -- evaporated during the course of Wednesday's mauling at San Siro.
A downcast Arsene Wenger described the result as a "disaster", and voiced concern that it could send Arsenal's season into an irretrievable nosedive unless his players responded swiftly.
"We have a big game on Saturday and it's an opportunity to show that we have character and mental strength, and that we can respond after such a shocking defeat," Wenger said.
"A big disappointment like that has consequences on your belief. We have a lot of work to regroup and not a lot of time to prepare for Saturday's game. We need to show something completely different on Saturday."
Chelsea, meanwhile, face a potentially awkward home tie against Birmingham City on Saturday, with manager Andre Villas-Boas struggling to maintain control of his squad after last weekend's 2-0 league reverse at Everton.
Villas-Boas reportedly faced an open revolt during a training ground bust-up last Sunday, when Chelsea's players were ordered to report for work on their day off as punishment for the performance at Goodison Park.
With billionaire Russian owner Roman Abramovich looking on, several senior Chelsea players are reported to have challenged Villas-Boas over his team selections, tactics and inability to respond to pressure.
Villas-Boas admitted this week that there had been a difference of opinion but denied "strong words" had been exchanged.
"That is normal," Villas-Boas said. "They don't have to back my project. It's the owner who backs my project."
The Portuguese manager also played down suggestions that he had lost the confidence of Abramovich.
"I don't think so, but it's a question that you will have to ask the owner," Villas-Boas said. "I think the owner has full trust in me and will continue to progress with the ideas that we have."
Liverpool will aim to move on from last weekend's Luis Suarez controversy when they entertain Championship (second tier) side Brighton at Anfield on Sunday.
The Merseysiders issued a flurry of apologies after Suarez defied club orders by declining to shake the hand of Manchester United defender Patrice Evra before last week's league battle, the first meeting of the clubs since Suarez returned from an eight-game ban for racially abusing Evra.
Suarez's handshake snub was widely condemned across football, with critics taking aim at the tawdry nadir of a saga that has tarnished Liverpool's reputation and raised questions about Kenny Dalglish's handling of the affair.
Liverpool veteran Jamie Carragher said the Reds were determined not to suffer an upset against the Seagulls, who famously beat Liverpool at Anfield during their run to the 1983 final.
"It's a massive game for us," Carragher said. "If we win, we'll be into the quarter-finals. And if you do well there, you're at Wembley again (for the semi-finals). It certainly keeps the season going."
In other ties this weekend, Stevenage Borough will aim to pull off the shock of the round when they entertain high-flying Tottenham Hotspur on Sunday.
"We're going to need some fortune," said Stevenage manager Gary Smith. "But we are capable of causing an upset at home. I do believe that.
"A victory would be unbelievable. There would be a tremendous amount of excitement around the place."
Fixtures (1500GMT unless otherwise stated):
Saturday
Chelsea v Birmingham City (1230), Everton v Blackpool, Millwall v Bolton Wanderers, Norwich City v Leicester City, Sunderland v Arsenal (1715)
Sunday
Crawley Town v Stoke City (1200), Stevenage Borough v Tottenham Hotspur (1400), Liverpool v Brighton and Hove Albion (1630)
Source: AFP
Source: AFP