With five matches played, a number of teams have already booked their place in the knockout stages of the Champions League, while others know that their interest in the competition will not extend beyond Christmas.
However, ahead of the sixth and final batch of encounters next month, there is still plenty to be decided.
Here, Sports Mole looks at the conundrums that are yet to be answered in each of the eight groups.
Group A
Real Madrid: Despite doing their best to throw away a four-goal advantage in Donetsk last night, the 10-time champions secured top spot in the group with a 4-3 victory.
Paris Saint-Germain: The French outfit thrashed Malmo 5-0 in Sweden, but their inferior head-to-head record means that although they have qualified, it will be the runners-up spot for Laurent Blanc's men.
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Shakhtar Donetsk: The Ukrainians currently hold the advantage where qualifying for the Europa League is concerned and that will be guaranteed if they win in Paris next time out.
Malmo: Should Donetsk slip up, all Malmo have to do to reach the Europa League is better their result. However, they will have to do so in the intimidating surroundings of the Bernabeu.
Remaining fixtures: PSG vs. Shakhtar, Real Madrid vs. Malmo (December 8)
Group B
Wolfsburg: The Germans have not lost any of their last 29 games at the Volkswagen Arena and if they can extend that record to 30 against Man United, their place in the last 16 will be secured.
Manchester United: Last night's mundane 0-0 draw with PSV has made it a tough assignment for United to qualify. A win in Germany will book top spot, but a draw or a loss would leave them requiring a favour from CSKA. The Europa League has already been guaranteed.
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PSV Eindhoven: A victory over CSKA books PSV's place in the knockout stage and they will win the group if the Wolfsburg vs. United encounter ends in a draw and they win by a three-goal margin.
CSKA Moscow: The Russians know that they have no chance of qualifying, but they still have the Europa League to play for. A win in Eindhoven would nail third spot.
Remaining fixtures: Wolfsburg vs. Man United, PSV vs. CSKA (December 8)
Group C
Atletico Madrid: A 2-0 win over Galatasaray saw Atletico advance last night, while another three points in Benfica next time out will secure top spot.
Benfica: The Portuguese side are also through and will win the group if they avoid defeat against Atletico in Lisbon thanks to their superior head-to-head record over the Spaniards.
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Galatasaray: The Istanbul-based outfit can no longer qualify for the last 16, but they can still reach the Europa League. To do so they must either beat or draw with Astana.
Astana: The minnows are a point behind Galatasaray, which means that only a win in Istanbul will do if they are to qualify for the Europa League.
Remaining fixtures: Galatasaray vs. Astana, Benfica vs. Atletico (December 8)
Group D
Juventus: The Italian champions wrestled back top spot thanks to their 1-0 win over Man City last night. Avoiding defeat away in Sevilla on matchday six will secure top spot for already-qualified Juve.
Manchester City: An impressive 3-1 win away in Sevilla during the fourth round of games saw City qualify, but they now find themselves second in the group after the loss in Turin. For that to change they must beat Monchengladbach at home and then hope that Sevilla do them a favour.
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Borussia Monchengladbach: The Bundesliga side know that if they can win at the Etihad Stadium, they will be in the Europa League.
Sevilla: As for Sevilla, they must claim maximum points from their home clash with Juve and hope that Man City get the better of Monchengladbach.
Remaining fixtures: Man City vs. Monchengladbach, Sevilla vs. Juventus (December 8)
Group E
Barcelona: The group's dominant force, Barca have collected 13 points from a possible 15, leaving them clear at the top. Luis Enrique's men travel to Leverkusen on matchday six.
Roma: The Romans play host to BATE in the Stadio Olimpico and will nail their spot in the last 16 with a win.
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Bayer Leverkusen: But, Leverkusen are level on five points with Roma and if they can somehow find a way of toppling defending champions Barca, the battle for second spot will intensify.
BATE Borisov: The Belarusians, who are only a point further back, are still involved as well. If they win away in Rome and Leverkusen fail to beat Barca, it will be Aleksandr Yermakovich's team that unexpectedly advance.
Remaining fixtures: Leverkusen vs. Barcelona, Roma vs. BATE (December 9)
Group F
Bayern Munich: The 4-0 demolition of Olympiacos not only secured Bayern's progression, it also saw Pep Guardiola's men ensure that they will finish top ahead of their trip to Croatia.
Olympiacos: The equation for the Greeks is simple - avoid defeat against Arsenal in front of their own supporters at the Karaiskakis Stadium and they will be in the last 16. Even a 1-0 or 2-1 loss would see them advance through.
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Arsenal: Win by two goals or more in Greece and the 2006 finalists will progress at the expense of their hosts. A 3-2 victory would also be enough by virtue of goal difference.
Dinamo Zagreb: The Croatians find themselves bottom of the group and are out. They cannot even reach the Europa League because of their inferior head-to-head record with the Gunners.
Remaining fixtures: Dinamo vs. Bayern, Olympiacos vs. Arsenal (December 9)
Group G
Chelsea: A win over Jose Mourinho's former club Porto at Stamford Bridge on matchday six will see Chelsea go through as group winners. A draw is also enough, but that does not guarantee top spot.
Porto: Were the Portuguese side to win in West London, they would go through as group winners. A draw or a defeat would open the door for Kiev to progress.
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Dynamo Kiev: The Ukrainians must beat Tel Aviv in Israel to secure their place in the last 16. If Chelsea vs. Porto ends in a draw, they will go through having topped the group.
Maccabi Tel Aviv: As the only side to have not claimed a point in the group stages, unsurprisingly Maccabi are out. They will only have pride to play for when they host qualification-hunting Kiev.
Remaining fixtures: Dynamo vs. Maccabi, Chelsea vs. Porto (December 9)
Group H
Zenit St Petersburg: Five wins from five outings has seen Andre Villas-Boas's men waltz through as group winners. A win in Gent on matchday six will secure the 100% winning record.
Gent: Looking to become the first Belgian side to advance beyond the group stages, Gent must beat Zenit to guarantee it. Anything less leaves the door ajar for third-placed Valencia.
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Valencia: The La Liga outfit know that they will at least be in the Europa League, but a win over bottom-placed Lyon will put the pressure on Gent. A loss against the French side will eliminate Valencia.
Lyon: Three-time quarter-finalists and one-time semi-finalists Lyon have just one point to their name, meaning that they are out and cannot even qualify for the Europa League.
Remaining fixtures: Valencia vs. Lyon, Gent vs. Zenit (December 9)
