Arsenal manager Arsene Wenger gives instructions during a training session in London on Monday. Arsenal are due to play FC Porto in a Champions League Group G match in Portugal on Wednesday. (Reuters)

London: Barcelona face the prospect of spoiling their record as the first club to play 400 European matches this week by becoming the first Champions League title holders to be eliminated at the group stage. The desire to avoid such ignominy and celebrate such a milestone with a victory at their Nou Camp stronghold will no doubt spur Barcelona to the win they need against Werder Bremen in group A on Tuesday.

Anything less than victory in the final round of group matches, and Frank Riijkaard’s side will hand the trophy over to another contender before even having a go at the knockout phase. There is no shortage of creditable aspirants to the crown, starting with Chelsea — the team that put Barcelona in this tricky spot.

Chelsea will watch from the comfortable vantage point of a home game against Levski Sofia, who have lost all five matches in group A, scored only once and conceded 15 goals. Only a huge upset and a Werder shock in Barcelona can rob Chelsea of top spot in the group. Arsenal, playing away to 2004 champions Porto in group G on Wednesday, could help produce a double shock if they and Barcelona were both to lose and end up in the Uefa Cup.

If there is a draw at Porto, the Portuguese side will go through with Arsenal, but CSKA Moscow are waiting to pounce if there is a winner. The Russian side can take one of the berths if they win at Hamburg SV, who have lost all their matches, and leap into second place.

Liverpool, the champions the year before Barcelona, return to the scene of their 2005 final victory over AC Milan in Istanbul to play Galatasaray on Tuesday with top spot in group C in the bag.

PSV Eindhoven are also through and Girondins Bordeaux, the team they entertain, have secured a Uefa Cup berth. Premier League pace-setters Manchester United, looking to win the European Cup for the third time, must at least draw at home against Benfica in group F on Wednesday to avoid the embarrassment of a second successive group stage elimination.

United should have gone into the match leading the group after beating Benfica 1-0 in Lisbon in September — avenging their shock group stage elimination by the Portuguese team last season — but a penalty miss by Louis Saha handed Celtic a 1-0 win and qualification in the all-British clash in Glasgow last month.

Wayne Rooney should give United the necessary inspiration but a defeat would send Benfica, their rivals in the final when they won the trophy for the first time in 1968, through instead. AS Roma host twice finalists Valencia needing a draw to be sure of finishing second in group D behind the Spanish heavyweights, who travel short of several first-choice players through injury and suspension.

If the in-form Francesco Totti’s team should lose at Rome’s Olympic Stadium, they could hand qualification to Shakhtar Donetsk, who must beat Olympiakos Piraeus away.