Matchday six of the Champions League brought the group stage to a close. Three teams -- Ajax, Bayern Munich and Liverpool -- qualified for the knockout phase with a 100% record while Chelsea, Manchester City and Manchester United ensured that the Premier League will be fully represented in the round of 16.

But not all of Europe's big clubs had it their way: Barcelona will join Borussia Dortmund in the latter stages of the Europa League, while AC Milan finished bottom of their group.

We asked Gab Marcotti, James Olley and Alex Kirkland to answer some of the big questions arising from this week's matches.

What caught your attention on matchday 6?

Marcotti: Porto vs. Atletico Madrid was obviously an old-school slugfest, right down to the brawls and the late goals. Porto were hard done by and Atletico confirm themselves as everyone's favorite villains. I also found it weird that RB Leipzig, with nothing to play for, beat Manchester City (who also had nothing on the line, but Pep Guardiola put out a good team). Liverpool showed that energy and fresh legs (as Jurgen Klopp said) can matter more than quality, if the mindset and motivation is right.

Olley: Thomas Tuchel getting angry. The 11 months he has been in charge of Chelsea have been an almost undiluted success, but, following on from a sticky patch in the league, he saw his team surrender top spot in Group H at the death as Zenit St Petersburg equalised in the 94th minute on Wednesday. Finishing in first place is never a guarantee of an easy round-of-16 draw, but Tuchel has bemoaned the Blues' sloppiness in "the details" of late and this is another example.

Kirkland: Barcelona's group stage elimination for the first time in 21 years. Yes, it felt inevitable -- they were never going to go to Munich and win, even with Bayern already through and the match being played behind closed doors -- but the manner of the 3-0 defeat was yet another reminder of just how far Barca have fallen. "This is our reality ... it has to be a turning point," coach Xavi said. Winning the Europa League would be a start, but let's not get ahead of ourselves: this Barca team might not even find themselves among the favourites for that competition.

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Who is your group-stage MVP and why?

Marcotti: Sebastien Haller. Duh. Not only did he score in every round -- with 10 goals in total, including four in one match at Sporting CP -- but he helped Ajax top their group with six wins out of six games. And, without him, I'm not sure they even qualify.

Kirkland: It's hard to look beyond Haller, who scored in all six of Ajax's group games -- a feat previously only achieved by Cristiano Ronaldo -- on his debut in the competition. Otherwise, it's the usual suspects such as Bayern Munich's Robert Lewandowski and Liverpool's Mohamed Salah. Real Madrid's group-stage success felt more collective than individual. Their outstanding players were dotted around the team and stepped up at key moments: Karim Benzema, Vinicius Junior, Toni Kroos and Eder Militao.

Olley: Haller is the obvious candidate. Alex and Gab make the case for him perfectly so for the sake of variety, I'll go for Ronaldo. The Manchester United star -- who is ranked No. 2 among the world's top forwards in ESPN's FC 100 for 2021 -- single-handedly dragged into the knockout phase, scoring three times against Atalanta as United took four points from the Italians when they deserved none. He even helped give caretaker boss Michael Carrick a winning start at Villarreal. He turns 37 before the round of 16 begins, and there is almost a constant danger of United overindulging him, but Ronaldo remains the man for the big occasion.

In light of the Super League breakaway attempt, does the Champions League show there is no need for change?

Kirkland: The climax to this group stage was genuinely thrilling, with big names like Barcelona, Dortmund, Milan and Sevilla eliminated and it felt like there were few games with nothing riding on them. Matches that the Super League's backers would prefer never to see take place threw up proper shocks: Young Boys beating Manchester United or Sheriff Tiraspol winning at the Bernabeu in September. But it's also true that the nature of the group-stage format mean those upsets don't tend to matter much -- United and Madrid both ended up topping their groups. What absolutely doesn't count as improvement is the catastrophic reform that UEFA plans to implement in 2024, abolishing the group stage in favour of a "Swiss model" league which will mean even less drama.

Marcotti: Well, it's changing format anyway as we move to the "Swiss model". Personally, I thought things were fine as they were in terms of groups-to-knockout format. Yes, there are some games of no consequence at the end. But just think how many of those we have in domestic leagues across Europe every week. In any case, the Super League wasn't ever really about format as much as it was about cost control, financial redistribution and access.

Olley: The current format is probably the most bloated version of the Champions League that can exist while still retaining a sufficiently competitive element throughout. It isn't ideal, but it looks better than the incoming "Swiss model." And, at the very least, the surprise results achieved by Sheriff, Young Boys and others only underline the flawed arrogance of the biggest clubs trying to make the European Super League a closed shop.

The round-of-16 tie you want to see is...

Marcotti: Real Madrid vs. Paris Saint-Germain would be tasty. And I would love the idea of Salzburg's young guns taking on the old master, Ralf Rangnick, at Manchester United.

Olley: Real vs. PSG would obviously be brilliant, but what about Chelsea vs. Bayern? Thomas Tuchel vs. Julian Nagelsmann, Chelsea back at Bayern in the stadium where they beat them to win the whole thing 10 years earlier. Maybe being back on German soil might even reignite Timo Werner...

Kirkland: Real Madrid vs. Paris Saint-Germain, please: it could be dubbed "the Kylian Mbappe derby," and it would be a chance to see what Carlo Ancelotti's Real Madrid are made of. Sure, they're top of a weakened LaLiga, but are they really much better than Zinedine Zidane's side were last year? This tie would help us find out. If not, I'll take Madrid vs. Chelsea, a rematch of last season's semifinal, for the same reason.