Paris: Barcelona coach Frank Rijkaard is unlikely to entertain thoughts of conspiracy theories ahead of arguably the club's most crucial fixture of the season at home to Werder Bremen on Tuesday.

Nevertheless, more than a few Catalan eyebrows were raised after Chelsea's 1-0 home defeat to Bremen rekindled the Germans' hopes and left Barcelona's Champions League future dependent on victory at the Nou Camp.

Anything less than three points, and Rijkaard will be lumped with an unenviable sobriquet; of seeing his side become the first reigning champions not to make it past the group stages.

With eight fixtures on Tuesday, Barcelona's hosting of the high-flying German outfit by far the highlight of the night.

Six knockout phase places are up for grabs over two nights of Champions League action, but only two places have to be settled on Tuesday, when the fight to finish top of the group will also top many teams' agendas.

Roma skipper Francesco Totti will aim to shoot his side into the knockout phase when they face Valencia, who are guaranteed to finish top of group D, at the Olympic stadium.

The on-form Serie A side need only a draw against the Spaniards to put their name into the December 15 draw for the knockout phase.

On paper, there is little danger for Roma. Even if Shakhtar Donetsk, who have a two-point deficit to Roma, beat Olympiakos in Greece Roma would qualify on the head-to-head rule.

In group C Liverpool and PSV Eindhoven have already taken the top two qualifying spots, while Bordeaux are heading for the UEFA Cup having secured third place ahead of bottom side Galatasaray.

The Turkish club will be playing for pride when they host Liverpool in Istanbul, where Reds' boss Rafael Benitez could hand Jerzy Dudek a start in goal as an appreciation gesture for his efforts against AC Milan on their way to victory in the 2005 final.

PSV meanwhile host Bordeaux knowing that because of Liverpool's superior head-to-head record they cannot finish first in the group. The race for first place in group B is wide open.

Bayern Munich and Inter Milan have already qualified but Hernan Crespo and co. will be hoping to close their two-point deficit to the Bundesliga giants when they meet in Munich.

Bayern need only a draw to secure top spot, but perhaps have their heads down having lost their lead of the Bundesliga when they were held to a 1-1 draw by lowly Borussia Monchengladbach on Saturday.

Sporting Lisbon, who sit third in group B, need only a draw at home against Spartak Moscow to finish third and join the last 32 of the UEFA Cup. Rijkaard meanwhile will know that if Barcelona fail to make the grade, it will be partly down to Chelsea.

Barcelona dropped two precious points when a late equaliser from Didier Drogba secured a 2-2 draw at the Nou Camp last month.

And Chelsea's capitulation to Werder Bremen last time out did Barcelona no favours at all.

Barcelona could only manage a 1-1 league draw with Levante on Saturday when Rijkaard rested Brazilian midfield maestro Ronaldinho.

Despite that setback, Barcelona were celebrating mildly on Sunday having stayed top of the league when Sevilla fell to a 2-1 defeat at Barcelona-based Espanyol.

And if any of Werder's notably tall players were watching Barcelona's increasingly shaky defence during the match, it would have given them plenty of hope of securing the draw they need to qualify.

Werder's players, including Brazilian-born playmaker Diego, appear to be up for the challenge - especially after taking the lead of the Bundesliga in timely fashion on Saturday.

"It is a dream for every footballer to play in a game like the one we have with Barcelona," said Diego.

"Two great teams are playing one another at the highest level and neither is the favourite. Barcelona are at home but we only need a point. It will be terrific," he said.