Champions League: 4 big questions as the knockout stage kicks off

The knockout stage of the 2023-24 UEFA Champions League season begins on Tuesday, when several of Europe's leading teams — including last year's winner Manchester City and record 14-time titlist Real Madrid — play the first leg of their two-match, total-goals-wins round of 16 series.

As usual, there are no shortage of questions heading into the business end of soccer's most important club competition, which concludes June 1 at Wembley Stadium in London.

Four of the biggest are below.

Can Manchester City repeat as champs?

Although Pep Guardiola's side won all six of their matches in the group stage, the holders haven't been totally convincing during their title defense so far. This isn't quite the same team that steamrolled to a historic "treble" of trophies last year, when the club's long-coveted first European trophy was accompanied by domestic honors in both the Premier League and FA Cup.

City sits second in the current Prem standings. Star striker Erling Haaland missed almost two months of the campaign with a foot injury. 

But Haaland is back now, and the Sky Blues got a favorable round of 16 opponent in Denmark's FC Copenhagen, which will visit the Emirates Stadium on Tuesday to open the home-and-home. Somewhat counter-intuitively, there's also less pressure on Guardiola this time around, what with City having finally gotten over the hump in the Champions League last spring.

In addition to still boasting probably the deepest and most talented roster in the sport, this is now a proven, grizzled, battle-hardened team. So while we haven't seen the best of the Cityzens so far, they're the bookies' consensus favorite for fairly obvious reasons. Time will tell if Man City can win for the second time running, but bet on this much: they won't relinquish the silverware without a fight.

Will Real Madrid add a 15th crown?

If any team knows how to turn it on in do-or-die Champions League matches, it's Real Madrid. Easily the most decorated club on the continent — with 14 European titles, Los Blancos have twice as many as Italy's AC Milan, the next most successful team — Real is still at the tail-end of its perhaps its greatest era: They've won the Champions League five times since 2014.

The most recent of those came two years ago. Real's squad has changed a lot since then, with the likes of longtime striker Karim Benzema and midfield rock Casemiro having left and brilliant young midfielder Jude Bellingham — acquired last summer from Borussia Dortmund — emerging as the new face of the club. But mainstays such as captain Nacho Fernandez, maestro Luka Modrić, winger Vinícius Júnior and midfielders Toni Kroos and Federico Valverde remain, providing both experience and stability.

Real's championship pedigree will be tested on Tuesday in Germany, when the Spaniards visit RB Leipzig. The visitors are the favorites, yet they've also struggled mightily to stay healthy lately. Nacho and Viní Jr. just returned from injury, and Bellingham will miss at least the first leg because of a sprained ankle. Still, this club always seems to find a way in this competition. City and Bayern Munich may have better odds, but it would surprise nobody if Real Madrid is standing on the podium once again when it's all said and done.

Is this PSG's Last Dance with Kylian Mbappé?

We still don't really know if these next few months truly represent Kylian Mbappé's swan song with Paris Saint-Germain, the French superstar/World Cup winner's hometown club. A week after Mbappé (once again) seemed destined to leave the Parc des Princes at season's end for longtime suitor Real Madrid, the deal (once again) appears to have fallen apart.

Whether Mbappé stays or goes this summer, this much is clear: PSG is running out of chances to win the title its wealthy Qatari owners have been obsessed with since buying the club and spending them into the contender class more than a decade ago. The closest the Parisians got was in pandemic-shortened 2020, when Mbappé, Neymar & Co. won a pair of single-elimination contests but lost the final to Bayern Munich.

Neymar left last summer. Lionel Messi has come and gone since then, too. Now the pressure is on Mbappé alone. And despite a commanding lead atop Ligue 1, it's fair to wonder if this PSG side is capable of making even a deep run, let alone going all the way. Still, while the first obstacle is significant — Real Sociedad of Spain, which visits the City of Lights on Wednesday, is no pushover — it's not a behemoth like Bayern, which ended PSG's campaign in the round of 16 a year ago.

Can Mbappé do it by himself this year? With 30 goals in 29 matches in 2023-24 already, maybe. He's the best player in the world, along with City's Haaland. What a story that would be.

More likely, though, is another disappointing finish that leaves Mbappé edging ever closer to the exit, and PSG wondering when — or even if — it will ever be good enough to capture Europe's ultimate prize.

Which other contenders could win the trophy?

With Harry Kane leading the line, Bayern has perhaps an even more potent threat up top than they did when Robert Lewandowski led them to their last Champions League triumph four years ago. (Bayern opens its knockout round slate Wednesday against Lazio in Rome.)

After a long absence from the competition, Arsenal has proven that they're the real deal, too. The Gunners might even have a better chance of winning the Champions League than the Prem, in which they trail first place Liverpool by just two points and really can't afford to not win every outing between now until May. Arsenal kicks off the round of 16 next week versus Porto.

Then there's Inter Milan, last year's runner-up. Inter is having another excellent season, though the Nerazzurri will have to outlast a strong foe in Atlético Madrid in its first knockout round series after finishing second in its group. 

Dortmund or the Netherlands' PSV Eindhoven probably can't win it all. But having been drawn against each other, one will advance to the quarterfinals. The same goes for another former European champ, rebuilding Barcelona, and Serie A holders Napoli. That should help make for a fascinating last eight, though plenty of games will be played before then.

Doug McIntyre is a soccer writer for FOX Sports. Before joining FOX Sports in 2021, he was a staff writer with ESPN and Yahoo Sports and he has covered United States men's and women's national teams at multiple FIFA World Cups. Follow him on Twitter @ByDougMcIntyre.