Beaten by Manchester United, which brought their 49-match unbeaten league run to an end, and fortunate to escape with a draw against Southampton on Saturday, the Gunners return to Champions League action against a Greek side who held them 2-2 in Athens two weeks ago.

While the Gunners' fate in Europe can't be decided on Tuesday, the Italian juggernaut of Milan rivals Inter and AC can storm into the knockout stages as both have 100-percent records.

Inter face Valencia, who they crushed 5-1 two weeks ago, while Milan go to Barcelona who they edged 1-0 in their first meeting thanks to deadly hitman Andriy Shevchenko.

Chelsea can also make sure of their place in the last 16 with a win against CSKA Moscow.

Arsenal's French international Robert Pires is aware of the pressure ahead of the Group E match at Highbury against the Greeks who were let off the hook two weeks ago thanks to two embarrassing blunders by goalkeeper Jens Lehmann.

"In my mind, winning the Premier League is a far greater achievement than lifting the Champions League," Pires said.

"Maybe the Champions League is more prestigious, but I believe the domestic league is the more accurate measure of the strength of a team.

"This is especially true in England, where the league is a physical challenge. You have to be on top of your game week in week out over 10 months."

If the statistics are any guide, the Gunners shouldn't worry too much on Tuesday as they have beaten Panathinaikos 2-1 on the Greeks' last two visits to London.

London rivals Chelsea have a perfect record in Group H and can make sure of a place in the knockout stages with a win in Moscow but the Stamford Bridge side's Russian star Alexei Smertin warned his team-mates to expect a frosty reception.

"CSKA are a good team and I think they can go a long way," said Smertin, who left rivals Lokomotiv Moscow to join Bordeaux in 1999.

"The minimum objective for us was to take nine points, and we have done that. Now, though, we have to go to Moscow - I hope that the weather will be good for us, but I expect it will be snowing!"

The night's glamour tie will be at the Nou Camp where Spanish league leaders Barcelona face AC Milan with the home side having suffered nightmares at the hands of their visitors in the competition down the years.

Barca were thrashed 4-0 by Milan in the 1994 final while a 2-0 defeat four years ago ensured the Spaniards didn't progress beyond that year's group stage.

"I am well aware of the history between the two clubs," said Barcelona coach Frank Rijkaard after their 1-0 defeat in Milan two weeks ago.

"But I think we showed enough in the San Siro to make sure that Milan will be thinking long and hard about the return game. Obviously, their big danger man is Shevchenko. We've got to keep him quiet."

Inter, who have drawn seven of the nine league matches this season, can do no wrong in the Champions League and victory at home to Valencia will clinch a place in the knockout stages.

"In the Champions League so far we have done very well, whereas in the championship we have been very inconsistent," said Inter's Brazilian striker Adriano.

"Perhaps we are more focused when it comes to playing in Europe. We played superbly in Valencia, we passed the ball around without any fear."

Valencia's Italian coach Claudio Ranieri, who was sacked by Chelsea in the summer, is desperate for a win and end a run of seven games without a victory.

"We are in the middle of a bad streak right now, but we are working hard to put things right," he said after Saturday's 1-1 draw with Atletico Madrid.

Celtic need a miracle to qualify from Group F having lost all their three matches but there is still hope.

In 2001, Newcastle lost their opening three games but won the next three to make the knockout stages.