The moment of truth is fast approaching for the 32 sides contesting this season's UEFA Champions League. Matchday 4 takes place over the course of Tuesday and Wednesday, with the English quartet well placed on seven points each and Barcelona, the only side still with a 100 per cent record, on the verge of advancing to the first knockout round.

Germany's two representatives, Bayern Munich and Werder Bremen, remain unbeaten after three matches, while Roma in Group A and Porto in Group G are the two big names in the greatest danger of making an early exit. And while Lyon look fairly comfortable in their section, compatriots Bordeaux and Marseille cannot afford to let any more points slip.

The big game
Roma-Chelsea, Group A, Stadio Olimpico, Tuesday 20.45 (local time)

Nothing is going right for Roma at the moment. Sunday's 2-0 defeat at Juventus was their fifth straight loss in all competitions and saw the one-time title aspirants plunge to 17th in Serie A, just one place above the relegation zone.

Luciano Spalletti's side are faring little better in Europe and need to take something from their home tie with Chelsea, who surged to the top of the Premier League at the weekend thanks to a thumping 5-0 win over Sunderland.

Yet to concede a goal in Group A, the Londoners could secure their place in next round if they win in the Italian capital. While they will have to make do without the injured Ricardo Carvalho, Didier Drogba is available once more and will be pressing for inclusion alongside the in-form Nicolas Anelka, the top scorer in England so far this season with eight goals.

The other games
In the other game in Group A, Romanian outsiders Cluj have the chance to strengthen their grip on second place when they entertain Bordeaux.

After going down to a solitary goal at the San Siro two weeks ago, Cypriot upstarts Anorthosis Famagusta will be out to maintain their hold on second place when they entertain Group B leaders Inter Milan. To do that, though, the islanders will need to bounce back from last weekend's heavy 4-0 league defeat to Omonia, their first home reverse in 39 games.

The other encounter in the section pits bottom-placed Panathinaikos against Werder Bremen, with the Germans no doubt hoping to reprise their 5-1 win over the Greeks three seasons ago.

With memories of their 5-0 thrashing at the hands of Group C frontrunners Barcelona still fresh, Basel face a daunting trip to the Nou Camp. The Catalans have strung together seven consecutive wins and now top the Spanish league. Victory over the Swiss coupled with a draw or a win for Sporting Lisbon at home to Shakhtar Donetsk will see the Azulgrana go though.

Liverpool and Atletico Madrid are both unbeaten in Group D and face off at Anfield with first place at stake and a possible ticket to the next round should Marseille beat PSV Eindhoven.

The situation is virtually the same in Group E, where Manchester United and Villarreal will both check into the last 16 if they win away to Glasgow Celtic and Aalborg respectively.

Bayern Munich are right back on form but will be handicapped by the absence of goalscorer Luca Toni for their awkward trip to Group F rivals Fiorentina. Three points for the Bavarians could take them over the line, however.

Two points behind them lie Lyon, who won in Romania a fortnight ago and are widely expected to complete the double over crisis-stricken Steaua Bucharest at home.

After shipping six goals in their last two league matches, much to the displeasure of Arsene Wenger, the Arsenal rearguard will be under close scrutiny when Group G opponents Fenerbahce drop in to North London.

In the other game in the section Porto travel to Ukraine intent on making amends for a damaging 1-0 reverse at home to Dynamo Kiev and maintaining a realistic chance of qualifying.

Buoyed by a morale-boosting 2-1 triumph over Real Madrid in their last outing, Juventus are in relaxed mood ahead of their Group H summit meeting at the Bernabeu. Fresh from lifting their third consecutive Belarussian title, Bate Borisov could yet cause the top two some problems, but will need to beat Zenit at home to stay in the hunt.

Player to watch
Simao Sabrosa has a good record against English sides, and Atletico Madrid will be hoping the Portuguese winger can keep his maintain his scoring form at Anfield. It was the former Barcelona man who slotted home Atletico's equaliser against the Reds two weeks ago, and in his Benfica days Simao also scored in a 2-0 win at Liverpool in the last 16 in 2005/06 and against Manchester United in the group phase that same season. To cap it all he converted both his penalties in shootout wins over England at UEFA EURO 2004 and the 2006 FIFA World Cup Germany™.

The stat
2 - The number of teams in this year's competition who have already sacked their coaches. Mircea Lucescu has made way for former Romania international Dorinel Munteanu at Steaua Bucharest, while Bruce Rioch was given his cards at Aalborg, with assistant coach Allan Kuhn standing in as his replacement until 1 January.

What they said
"They are young and they need to be guided." Arsenal coach Arsene Wenger explains how he intends to get his players back on track.

Have your say
Will Barcelona win all six of their group matches? Can Bayern Munich clinch qualification in Florence? Click on ‘Add your comment' and tell us what you think.