Arsenal have not failed to get beyond the group stage of the Champions League since 1999 but their hopes of progressing this year will be on the line when they face Bayern Munich on Tuesday night.
Defeats to Dinamo Zagreb and Olympiakos have left Arsene Wenger's men on the ropes ahead of the toughest assignment in Group F - back-to-back fixtures against Pep Guardiola's Munich side.
Domestic form has been encouraging - Arsenal sit second in the Premier League - but time is running out in Europe.
"We have some ground to make up in Europe as we have not been at our requested level in our first two games," said Wenger.
"Our focus has been much stronger in the Premier League than it has been in Europe and we know in this game the focus needs to be exactly the same than in the Premier League."
Arsenal sit bottom of the group, with Bayern on six points and Olympiakos and Dinamo level on three points before their meeting in Zagreb.
Roma are another team under pressure after their shock 3-2 loss to BATE Barisov left them bottom of Group E despite a creditable draw against Barcelona in the opening round.
The Italians head to Germany to face Bayer Leverkusen on Tuesday, and Leverkusen coach Roger Schmidt is wary of the wounded animal.
"We know that Roma are under pressure after their defeat in Borisov," he said.
Barca head to Belarus on a back of a 5-2 win over Rayo Vallecano in which Neymar scored four times.
Among the victims of Chelsea's poor start to the season has been star man Eden Hazard, who was benched for the 2-0 win over Aston Villa amid criticism from Jose Mourinho.
The English champions, beaten 2-1 by Porto last time out, are in Ukraine to face Dynamo Kiev, and Mourinho refused to say if Hazard would return.
"If he plays tomorrow I don't tell you. The players don't know," Mourinho said.
Dynamo are level with Porto on four points at the top of the group, one ahead of Chelsea with Maccabi Tel Aviv yet to register ahead of their match in Portugal.
Lyon are another side already facing an uphill battle to stay in the competition with only one point from their opening two matches and a trip to group leaders Zenit St Petersburg - and the frigid Russian conditions - on the agenda
Goals - or a lack thereof - have been Lyon's undoing so far this season, with only 12 in 10 Ligue 1 outings and only one in their two Champions League matches.
"It's obvious that it's hard for us to score these days," coach Herbert Fournier said.
"We need to play more freely if we want to continue our Champions League dream."
Valencia host Gent in the other Group H fixture.
Arsenal and Chelsea will both feature live on BT Sport on Tuesday night, with Arsenal's crunch game on BT Sport Europe and the Blues' trip to Kiev to be live on BT Sport 2.
