Manchester United and Real Madrid are among the teams facing the possibility of an early Champions League exit in this week’s final round of group games.
United, who were knocked out in the group stage in 2015-16, must avoid defeat against RB Leipzig on Tuesday to guarantee progression to the last 16.
And 13-time European champions Real – who have never been knocked out at the group stage – need a victory over Borussia Monchengladbach on Wednesday to progress for the 23rd year in a row.
Chelsea, Liverpool, Manchester City and holders Bayern Munich are among the nine teams through to the knockout stages.
Here is the state of play going into the final round of group matches on 8 and 9 December.
Who is through to the knockout stages?
Qualified (but final position to be decided): Barcelona, Borussia Dortmund and Juventus
Guaranteed top spot: Bayern Munich, Chelsea, Liverpool and Manchester City
Guaranteed second: Porto and Sevilla
Who still has something to play for?
Group A: Atletico Madrid, Red Bull Salzburg
Group B: Borussia Monchengladbach, Shakhtar Donetsk, Real Madrid, Inter Milan
Group D: Atalanta, Ajax
Group F: Lazio, Club Bruges
Group H: Manchester United, Paris St-Germain, RB Leipzig
When is the last 16 draw and how does it work?
The draw for the last 16 will take place on Monday, 14 December at Uefa’s headquarters in Nyon, Switzerland.
Teams finishing top of their group will be drawn against a team finishing second in a different group.
Clubs cannot face a side they met in the group stage and, at this stage of the competition, teams from the same country cannot be drawn against each other. That is allowed to happen from the quarter-finals, the draw for which takes place on 19 March, alongside the semi-finals.
Teams will then be able to plot their route to the final, which is on 29 May at the Ataturk Olympic Stadium in Istanbul.
The last-16 ties are two-legged and will take on 16/17 and 23/24 February, and 9/10 and 16/17 March.
What do sides need to do to qualify?
Group H – What do Man Utd need?
Tuesday, 8 December – Paris St-Germain v Istanbul Basaksehir, RB Leipzig v Manchester United (both 20:00 GMT)
Results in matchday five mean it is extremely tight at the top of Group H.
United need a point away at RB Leipzig to qualify for the last 16. A defeat in Germany would see them drop into the Europa League.
They could win the group with a point (if PSG do not win at home against Istanbul Basaksehir) but if PSG win their match they will top the group no matter the United result.
Leipzig will be through with a win. If they draw, they need PSG to lose.
If both United and PSG lose then the Parisians will qualify (alongside Leipzig) courtesy of a better goal difference in the two games between them and United.
Group B – Real on the brink?
Wednesday, 9 December – Inter Milan v Shakhtar Donetsk, Real Madrid v Borussia Monchengladbach (both 20:00 GMT)
Another group that is wide open is Group B with all four teams still able to qualify. Leaders Borussia Monchengladbach travel to Real Madrid. If either side wins they are guaranteed to go through. The Germans will also progress with a draw. A point would only be enough for Real if Inter beat Shakhtar because of their superior head-to-head record over the Italians but not the Ukrainians.
A win takes Shakhtar through, and they would also progress with a draw if Real do anything but win. Inter have to win to reach the last 16 and even that would not be enough if the other game ends in a draw.
What about the other groups?
Atletico Madrid will progress from Group A providing they avoid defeat against Red Bull Salzburg in Austria (9 December, 20:00 GMT).
They will be joined by Atalanta, if they do not lose against Ajax (9 December, 17:55 GMT), and Lazio as long as they pick up a point against Club Bruges (8 December, 20:00 GMT).
If Lazio win then Borussia Dortmund will need to beat Zenit St Petersburg to guarantee finishing top of Group F.
Barcelona will secure top spot in Group G if they do not lose by more than one goal to Juventus. A 2-0 defeat would see them stay top, but Juve would top the group if they won 3-1, 4-2 etc or by more than two goals.
Which sides cannot reach the knockout stages?
The following sides are definitely out of last-16 contention. Krasnodar have guaranteed a Europa League spot for finishing third, while FC Midtjylland, Rennes, Zenit and Istanbaul Basaksehir will all finish fourth in their groups. The others can all still reach the Europa League.
Group A: Lokomotiv Moscow
Group C: Olympiakos, Marseille
Group D: FC Midtjylland (will finish fourth)
Group E: Krasnodar, Rennes (will finish third and fourth respectively)
Group F: Zenit St Petersburg (will finish fourth)
Group G: Dynamo Kyiv, Ferencvaros
Group H: Istanbul Basaksehir (will finish fourth)
What about the Europa League?
Arsenal, Leicester City, Tottenham and Rangers have booked their place in the Europa League last 32. Here are the qualifiers from each of the groups so far:
Group A: Roma
Group B: Arsenal
Group C: Slavia Prague, Bayer Leverkusen
Group D: Rangers, Benfica
Group E: Granada, PSV Eindhoven
Group G: Leicester City, Braga
Group H: Lille, AC Milan
Group I: Villarreal
Group J: Royal Antwerp, Tottenham
Group K: Dinamo Zagreb
Group L: Hoffenheim, Red Star Belgrade