Twelve teams have already booked their place in the Champions League round of 16 after the last set of group games. Who will be the last four teams to join them?
Here is a look at what is still undecided heading into Matchday six:
Both Atletico Madrid and Borussia Dortmund have already qualified for the knockout stage, with Club Brugge third and dropping into the Europa League. Thierry Henry’s Monaco have been eliminated.
Atletico will secure top spot, and with it seeding for the last-16, if they beat Brugge or Dortmund fail to win away at Monaco.
Should the Germans win and the Spaniards lose in Belgium, then Dortmund would progress as group winners by virtue of their superior head-to-head goal difference.
Barcelona are through as group winners, while both Tottenham and Inter Milan can also still join them in the last 16. Dutch club PSV Eindhoven will finish bottom.
Spurs are currently second on head-to-head away goals, so will progress if they win in the Nou Camp or match, points-wise, Inter’s result at home to PSV.
The most complicated of possible outcomes means current group leaders Napoli, second-placed Paris St Germain and Liverpool, in third, can still all qualify. Red Star Belgrade are bottom of the table, but could yet make it through to the last 32 of the Europa League.
Liverpool host Napoli and must win to have any chance of going through — victory by more than one goal will ensure qualification.
Should PSG beat Red Star away, Jurgen Klopp’s men will need a 1-0 triumph or victory by two goals or more to finish second behind the French side, but other win margins will not be enough.
If the game in Belgrade is a draw, Liverpool will advance with any win as it would leave them, PSG and Napoli all on nine points — with the English club finishing first on the three-way head-to-head.
Red Star will take third place if they win and Liverpool lose.
Porto are through as group winners, while Schalke will progress as runners-up.
Galatasaray will finish third if they win at home against Porto or if Lokomotiv Moscow do not beat Schalke away.
The Russians will be through if they win and Galatasaray do not beat Porto.
Bayern Munich and Ajax have both qualified for the last 16, while Benfica will be in the Europa League and AEK Athens are out.
The Germans can secure first place with a draw away to Ajax, who can themselves finish top with victory in Amsterdam.
Manchester City currently lead the group by three points from Lyon and have already made sure of qualification.
French side Lyon and Shakhtar Donetsk can also both still progress, while Hoffenheim are in with a chance of a spot in the Europa League.
City will seal top spot with a draw at home to Hoffenheim or if Lyon do not win away at Shakhtar.
Lyon can take first place in the group with victory and if City lose, as they hold a better head-to-head record over the Premier League champions.
Ukrainian side Shakhtar, currently on five points, will progress if they beat Lyon. A draw or Hoffenheim failing to win would see them into the Europa League round of 32.
German club Hoffenheim, who have three points, must win and then hope Shakhtar lose at home to Lyon to sneak into third place.
Real Madrid have qualified as group winners, with Roma through in second place.
Viktoria Plzen and CSKA Moscow both have four points, but the Czech club are third based on their superior head-to-head record.
The Czechs can secure a Europa League place if they match CSKA’s result, while the Russians, away to Real Madrid, must pick up more points than their rivals to progress.
Juventus currently top the group, two points ahead of Manchester United, with both teams already qualified for the last 16. Valencia will finish third, while Young Boys are eliminated.
The Italians will secure first place if they win in Switzerland, while United will progress if they beat Valencia away and Juventus fail to take maximum points.