The cream of Europe have risen to the top of their Champions League groups and qualification is in sight for six teams heading into the fourth round of matches in the competition.
A slew of weaker teams, meanwhile, are likely to be eliminated this week as the picture becomes clearer in the group stage.
Here are five things to know about this week's games in Europe's top competition.
SPANISH TEAMS LEADING LAST-16 CHARGE
Of the sides who can reach the knockout stage with two games to spare this week, three of them come from Spain.
Real Madrid and Atletico Madrid both boast 100 percent records and would qualify for the last 16 with wins -- or possibly draws -- against Juventus and Austria Vienna, respectively. Barcelona would also seal a top-two finish in Group H by beating AC Milan at Camp Nou and if Ajax wins at home against Celtic.
Paris Saint-Germain is a strong favorite to advance in Group C with a victory over Anderlecht, with the French team having won 5-0 in Belgium two weeks ago.
And reigning champion Bayern Munich would also be in the last 16 with a win over Viktoria Plzen, provided CSKA Moscow doesn't beat Manchester City away elsewhere in Group D. A City win puts the English team through in that scenario, too.
ARSENAL IN DANGER
It's not going smoothly for all of Europe's so-called heavyweights, though.
Premier League leader Arsenal may also top Champions League Group F but the 2-1 loss to Borussia Dortmund last time out could be costly. Another reverse against last season's beaten finalist on Wednesday, and Arsenal may need to beat Napoli -- the other contender in the group -- in Italy to go through. The three teams are currently all on six points.
AC Milan's progress is also far from secure if, as is likely according to recent history, the Italian team loses at Barca on Wednesday with Celtic and Ajax ready to challenge.
The likes of Plzen, Real Sociedad, Anderlecht and Marseille, who are all bottom of their groups, are expected to be knocked out of contention this week.
TIKI-TAKA AT PSG
Barcelona may be losing its tag of the pass-masters of Europe.
According to UEFA statistics, Paris Saint-Germain is the team that has attempted (2,477) and completed (2,135) the most passes in this season's Champions League. PSG coach Laurent Blanc promised a more entertaining brand of football than what was produced under Carlo Ancelotti last season, and he is proving true to his word.
The new approach is paying off, too. PSG is tied with Real Madrid for the most prolific attack in the competition (12 goals scored) and also has the joint-best defensive record with Bayern Munich and Barcelona, conceding just one goal.
PSG tops a weak Group C with a five point-lead over Olympiakos and Benfica and just needs a victory over Anderlecht at Parc des Princes on Tuesday to secure qualification for the knockout phase. Zlatan Ibrahimovic, who scored four goals in the 5-0 hammering of Anderlecht in Belgium on Oct. 23, is a doubt because of a left knee injury.
RONALDO UPSTAGING MESSI
Cristiano Ronaldo is guiding a Real Madrid attack so potent it left a Rayo Vallecano player in tears during Saturday's 3-2 win. Lionel Messi, meanwhile, is struggling to get Barcelona firing.
Ronaldo, Gareth Bale and Karim Benzema have combined for 10 goals in two league games, with Ronaldo particularly dangerous since Sepp Blatter's slight against him. The Portugal international has scored 20 goals in 15 games this season and needs just two more in the Champions League with three games to go to set a group-stage record with nine goals.
Messi has 12 goals from 12 games this season but the Argentina forward is still not fully recovered from a leg injury, with uncharacteristic turnovers plus missed scoring opportunities the proof. He has gone four consecutive La Liga games without a goal for the first time since the 2010-11 season.
HANGOVER OF RACISM ROW
The specter of racism hangs over the return fixture between Manchester City and CSKA Moscow after the Russian champions were punished by UEFA for their fans' "racist behavior" during City's 2-1 win in Moscow two weeks ago.
CSKA must play its next home match, against Bayern Munich, in a partially closed stadium as a sanction for the abuse City's black players suffered in what proved to be a high-profile disciplinary case.
It means there will be heavy scrutiny on CSKA's visiting supporters at Etihad Stadium on Tuesday.