Former champions AC Milan and Borussia Dortmund go into their final group matches needing a result in their respective games to ensure they continue their campaign for the trophy in the New Year.
AC Milan need only a point against Ajax today to secure entry to the last 16 of the Champions League, but embattled coach Massimiliano Allegri is taking nothing for granted.
For the second consecutive season Milan's run-in to Christmas is anything but festive: they currently sit ninth in Serie A, 22 points behind leaders Juventus and 14 adrift of the first Champions League qualifying spot.
With Ajax conceding only three defeats on their way to second place in the Dutch top flight, Allegri says it would be a mistake to underestimate Frank De Boer's side, who, with a win, would qualify.
"Ajax have shown some great form of late and they have great technique throughout the team. We have to have the right attitude against them and, above all, score goals," said the Italian.
Milan's 3-0 rout of Celtic in Scotland a fortnight ago, when Ajax stunned Barcelona 2-1 in Amsterdam to stay in contention, kept the Italian giants in second place in Group H with a one-point lead on the Dutchmen.
It means the seven-time European champions need just a point at the San Siro to join leaders Barcelona in the knockout phase.
Meanwhile, Barcelona welcome Celtic to the Camp Nou still needing a point to mathematically ensure they finish top of Champions League Group H.
The Catalans appeared to be cruising to first place and the benefit of having the second-leg of their last 16 tie at home having beaten AC Milan 3-1 to qualify on matchday four.
However, a 2-1 defeat away to Ajax in their last European outing leaves them just two points clear of Milan.
Defeat in Amsterdam was followed by another loss, this time on the domestic front, as Athletic Bilbao ended Barca's 26-game unbeaten run in La Liga five days later.
Despite the group stage's predictable nature, this season has at least proved more competitive than last term when 13 of the 16 knockout stage places had been booked before the final round of group matches.
As expected, Group F has turned out to be by far the toughest.
Leaders Arsenal (12 points) travel to Napoli (9) needing a draw, or a defeat by less than three goals, while Borussia Dortmund (9), will go through if they beat pointless Olympique Marseille away, regardless of the other result.
Should Napoli and Dortmund both win, they will finish level with Arsenal on 12 points and the qualifiers will be decided by the results between the three teams.
Group E will also have a dramatic finish when habitual over-achievers Basel (8 points) visit spectacularly inconsistent Schalke (7) needing a point to join Chelsea in the last 16.
Despite their dismal domestic form, seven-times champions AC Milan (8) should get the point they need at home to Ajax Amsterdam (7) and follow Barcelona through from Group H.
"The Dutch have achieved great results and have good technique and we must take all the necessary precautions," said Milan's unflappable coach Massimiliano Allegri whose future is the source of constant speculation.
"We have to score a goal, we cannot think of playing for the 0-0."