Champions League titleholder FC Barcelona is in an uncomfortable position heading into this week's penultimate round of the group stage.
Barcelona is third in Group A and needs to win at Levski Sofia tomorrow to stay in contention for the second round.
But if Barcelona draws or loses -- and if Werder Bremen beats Chelsea in Germany -- the Spanish club is out.
"It's on the minds of all the players because we are aware that we have two [important matches] ahead of us," Barcelona captain Carles Puyol said.
Barcelona's final group game is against Bremen at Camp Nou on Dec. 5.
Chelsea leads Group A with 10 points, followed by Bremen with seven, Barcelona with five, and Levski on zero.
Levski shouldn't be a problem for Barcelona -- it beat the Bulgarian club 5-0 earlier. But the Spanish champion has also drawn Bremen 1-1, drawn Chelsea 2-2 and lost 1-0 to the English champion.
Barcelona beat Arsenal for its second European Cup title in May.
Chelsea has already advanced to the second round, along with Bayern Munich in Group B and Valencia in Group D.
Bayern is at Spartak Moscow tomorrow and can clinch first place in Group B with a win. Italian league leader Inter Milan will join the German team with a win over visiting Sporting Lisbon.
Valencia hosts Olympiakos tomorrow and will be joined in the next round by AS Roma if the Italian club beats Shakhtar Donetsk. Roma warmed up with a 7-0 win over Catania in the Serie A on Sunday.
In Group E, nine-time champion Real Madrid and Lyon compete for the top spot in Spain today. Both have already advanced.
Lyon is the only club in the competition to have won all four of its qualifying matches -- including a 2-0 home win over Real Madrid.
"Real Madrid will be out for revenge," Lyon midfielder Juninho said. "But we are going there to play our own game."
Lyon has yet to concede a goal in the Champions League.
"We're not going there for a draw or to defend, we're going there with enthusiasm, self-belief and the will to win," Lyon coach Gerard Houllier said.
Real Madrid will be without Ronaldo, who has a knee injury. Midfielder David Beckham is doubtful with a left knee problem.
Liverpool and PSV Eindhoven have advanced from Group C, but the order hasn't been decided.
Liverpool, virtually out of contention for the English title, hosts PSV, and Bordeaux welcomes Galatasaray on Wednesday. Liverpool was also struggling in the English Premier League when it won last year's Champions League title.
Groups F, G and H should begin to look clearer after this week.
CSKA Moscow, fresh from securing the Russian title, can advance with a win over visiting FC Porto today, when Arsenal hosts Hamburg, which has yet to earn a point. CSKA has eight points in Group G, and Arsenal and Porto both have seven.
Manchester United had an expected loss to FC Copenhagen in the previous rotation, but is confident it can beat Celtic in Glasgow today.
A win will be enough to ensure Man United the top spot in Group F, while a draw will secure qualification to the next round. United leads with nine points, followed by Celtic on six, and Benfica and Copenhagen at four each.
AC Milan needs only a point at AEK Athens today to advance, while a win would secure Group H. Lille can also go through if it beats Anderlecht and AEK loses. Milan has 10 points, Lille five, AEK four and Anderlecht two.