In the interim, Lionel Messi won his first World Cup title. Kylian Mbappe almost won his second, then got injured. Early-season favorites for the European title fell into slumps at home.
Meanwhile, one standout team before the World Cup, Napoli, has marched on and aims for its first quarterfinals place in the competition's 68-year history.
Off the field, the Super League project that tried to effectively kill the Champions League met a serious legal setback, and English title holder Manchester City faces Premier League charges of financial wrongdoing that can one day stop the club entering future Champions Leagues.
It adds up to plenty of drama even before soccer's most prized club competition resumes with a stellar game between Paris Saint-Germain and Bayern Munich.
A rematch of the 2020 final won by Bayern pairs two powers that helped stop the Super League in 2021 by refusing to join it. What it won't have at Parc des Princes are the goalscorer and goalkeeper with the best records from the group stage.
Mbappe, who scored seven goals across five different Champions League games in the fall, is out most of February with a thigh injury.
Bayern goalkeeper Manuel Neuer's season is over because he broke a leg skiing on a vacation taken after Germany's quick exit from the World Cup.
The other game Tuesday pairs AC Milan and Tottenham, two of the seven round of 16 teams that are currently outside the Champions League qualifying places in their domestic leagues. Chelsea is another and visits Borussia Dortmund on Wednesday, when Club Brugge hosts Benfica.
Four more first-leg games are scheduled Feb. 21-22.
At age 35, Messi finally has a World Cup title for Argentina. Now back to the business of winning a fifth Champions League.
When Messi won his fourth title with Barcelona in 2015 Barack Obama was president, Britain was in the European Union and Jose Mourinho won a league title, at Chelsea.
Messi has not been to the final since and his first try with PSG ended in the round of 16 against Madrid. When he last faced Bayern it was an 8-2 rout over Barcelona in the single-leg quarterfinals of the pandemic-hit 2020 edition.
Both PSG and Bayern have misfired since the World Cup. PSG was unbeaten entering 2023 then lost three in the league and is out of the French Cup. Bayern still leads the Bundesliga after restarting with three straight draws.
TEAMS IN SLUMPS
A Champions League adage is the team you draw after the group stage is not always the one you meet in February.
When the last-16 draw was made on Nov. 7, Real Madrid was the unbeaten Spanish league leader paired with an already inconsistent Liverpool. Madrid has now lost three of eight and let Barcelona take a dominating lead.
At least second-placed Madrid is so far clear of fifth in La Liga to be almost sure of qualifying for next season's Champions League.
Not so, Chelsea, Tottenham and Liverpool. Nor AC Milan, Leipzig, Eintracht Frankfurt and Club Brugge. None is currently on track to qualify for next season's competition.
For Liverpool and Chelsea, European champions in 2019 and 2021, actually winning another final on June 10 in Istanbul might be their best chance of being in the group-stage draw in August. That should be worth about 100 million euros ($107 million) in UEFA prize money.
That cash now looks almost essential to Chelsea after a season of lavish transfer spending signed off by American owner Todd Boehly.
Chelsea plays a Dortmund team third in the Bundesliga, just three points behind Bayern, without yet seeming a convincing title challenger.
Dortmund already has a great comeback story: Sebastien Haller's return from a cancer diagnosis and chemotherapy treatment.
Haller should make his European debut for Dortmund eight months since he was the club's marquee summer signing to replace Erling Haaland.
Haaland had five goals for Manchester City in the group, including in a 2-1 home win over Dortmund. He must wait another week to travel back to Germany for the first leg against Leipzig.
Napoli and Benfica topped their groups in November _ ahead of Liverpool and PSG, respectively _ to be seeded in the draw and avoid teams like Madrid, Bayern and Man City. Napoli travels to Eintracht Frankfurt on Feb. 21, and Benfica plays Wednesday at Brugge.
Both are set up for domestic titles after strong returns from the World Cup break. Could an elusive Champions League title follow? Benfica has not been European champion since 1962, Napoli never got close.
However, Napoli mostly stayed out of January trading while Benfica sold Argentina midfielder Enzo Fernandez to Chelsea for a British record fee of about 120 million euros ($128 million).
Benfica should have enough to eliminate Brugge, which fired coach Carl Hoefkens in December after poor domestic results despite overachieving in the Champions League. Brugge hired Scott Parker, whose previous game had been a 9-0 loss at Liverpool in August with Bournemouth.
Back in November, Barcelona and Juventus failed to advance out of the Champions League groups as they and fellow Super League rebel Madrid awaited news of their legal challenge to UEFA at the European Court of Justice in Luxembourg.
The court's initial non-binding opinion in December was to disagree with the clubs' claim that UEFA has monopoly control of European competitions. The final ruling of 15 judges is expected in weeks.
Barcelona now leads La Liga and has a stellar game this week with Manchester United in the Europa League knockout playoffs.
Juventus, which hosts Nantes on Thursday, has other issues _ a 15-point deduction in Serie A during a criminal investigation of alleged false accounting that led to the board of directors resigning.
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