Barca, Atletico in danger of early Champions League exit
Xavi Hernandez faces his first critical test as Barcelona coach with the club at risk of failing to make the Champions League knockout stages for the first time in two decades.
A goalless draw at home to Benfica last month left Barca with their destiny in their own hands, but with a much trickier final game away to Group E winners Bayern Munich.
Spanish champions Atletico Madrid have their work cut to secure one of the five unclaimed last-16 tickets after three defeats on the spin, while all four teams remain in the hunt in an unpredictable Group G.
Ballon d'Or backlash from Bayern?
Barca find themselves on the ropes ahead of Wednesday's trip to Germany, but it could have been far worse were it not for Benfica forward Haris Seferovic's glaring miss in stoppage time at Camp Nou.
Bayern are one of three teams with a perfect record in this season's competition, and Robert Lewandowski's perceived Ballon d'Or snub may give the star striker extra incentive to prove a point.
Xavi suffered his first defeat as Barca coach on Saturday against Real Betis. He rested key players with a view to the game in Munich, where victory would guarantee Barca go through as runners-up in Group E, extending their 20-year run of reaching the knockout phase.
A youthful Xavi was establishing himself as a mainstay of the midfield when Barca exited in the first group stage of the 2000-01 competition.
Failure to secure maximum points would open the door for Benfica to pip them to second place, with the Portuguese needing to beat Dynamo Kiev in Lisbon.
Three-horse race and four-way showdown
Porto, AC Milan and Atletico will battle it out for the second qualification spot behind Liverpool in Group B.
Two-time former European champions Porto hold a one-point edge over both rivals ahead of the visit of Atletico. Milan host a Liverpool side that Jurgen Klopp could rotate heavily ahead of a busy festive schedule.
Last season's Europa League winners Villarreal, beaten at home by two late Manchester United goals on matchday five, go to Atalanta knowing they will advance at the expense of the Italians if they avoid defeat in Bergamo.
Austrian champions Salzburg appeared to be coasting through after accruing seven points in three games, but back-to-back away losses mean they could still miss out.
Lille top Group G with eight points and will progress if they get a point at Wolfsburg. The Germans are last in the section but victory would send them through instead.
Salzburg can seal a knockout berth with a draw at home to Sevilla, who in turn would qualify if they win.
Already in the last-16 pot
Eleven clubs are assured of their place in the last-16 draw on December 13, five of which have already clinched top spot.
Erik ten Hag's impressive Ajax will attempt to complete a perfect group stage for the first time in club history at home to Sporting, certain of second above Borussia Dortmund irrespective of Tuesday's results.
Manchester City cannot be caught by Paris Saint-Germain in Group A, while Real Madrid have a two-point lead over Inter Milan in Group D ahead of their Bernabeu showdown.
Holders Chelsea, who go to Zenit Saint Petersburg for their final Group H game, will nail down top spot if they match Juventus' result at home to Swedish outfit Malmo.
Ralf Rangnick made a winning start to his spell as United's interim manager and is safe in the knowledge his team will move on as winners of Group F come what may against Switzerland's Young Boys.
Europa League consolation
All third-placed clubs will drop into the Europa League, but a revised format now sees them face the group runner-ups from the second-tier tournament in a play-off round before the last 16.
Sheriff Tiraspol, losers of three straight games after shocking Real in September, will continue their European adventure in the Europa League, as will Dortmund and Zenit.
RB Leipzig look favourites to finish third behind City and PSG despite parting ways with coach Jesse Marsch. The Germans are level on points with Club Brugge but have the head-to-head advantage prior to their home game with Pep Guardiola's side.