'Don't be so sure': Warning for European pretenders ahead of Champions League quarter-finals

Barcelona, Paris Saint-Germain and Arsenal hold such commanding leads in their Champions League quarter-final matches that a place in the last four looks all but certain.

Don't be so sure.

European club football's most prestigious competition has a habit of upsetting the odds.

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Barcelona and PSG have very recent memories of how quickly things can change.

Barcelona was 4-2 up on aggregate against PSG early in the second leg of last year's quarter-finals - only to lose 6-4.

In 2017 PSG led 4-0 after the first leg of a round of 16 game between the two in Paris, but famously lost 6-1 at Camp Nou.

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Part of what makes the Champions League such compelling viewing is the fragility of even the most commanding leads.

Liverpool trailed AC Milan 3-0 at halftime of the final of 2005 before staging a dramatic fightback and going on to win in a penalty shootout.

The Merseyside club stunned Barcelona on its way to the title in 2019 when overturning a 3-0 loss in the first leg of the semi-finals by winning the return leg 4-0.

There are many more examples of how the tables can be turned when Europe's elite go head-to-head, which is why nothing can be taken for granted ahead of this week's second leg matches.

Real trouble

Record 15-time winner and defending champion Real Madrid will have to produce another of its famous comebacks to overturn a 3-0 first leg loss to Arsenal.

If anyone can, Madrid can - but it goes into Thursday's (AEST) game at the Bernabeu after a run of unconvincing results.

Carlo Ancelotti's team has only won one of its last four games in all competitions - Monday's (AEST) 1-0 victory against Alaves.

The defeat to Arsenal could have been even heavier after being dominated at the Emirates Stadium and came after Madrid needed a penalty shootout to overcome Atletico Madrid in the round of 16.

But Madrid's history is built on producing special performances in Europe.

Its run to the title in 2022 was filled with dramatic comebacks - none more so than the semi-finals win against Manchester City when trailing 5-3 on aggregate going into the 90th minute of the second leg.

Madrid simply never knows when it is beaten.

Europe's finest?

This could be the first great Barcelona team of the post-Lionel Messi era.

Top of the Spanish league and on the verge of the Champions League semi-finals, Barcelona looks like the team to beat in this year's competition.

Leading 4-0 against Borussia Dortmund, it would take the unlikeliest of collapses in Germany on Wednesday (AEST) to prevent Hansi Flick's team from booking its place in the semi-finals.

With the devastating goal scoring power of Robert Lewandowski and the individual brilliance of Raphinha and Lamine Yamal, this looks like Barcelona's best team since the days of Messi, Neymar and Luis Suarez and its best chance in a long time of winning its first Champions League title since 2015.

A new era

The post-Kylian Mbappe era is going just fine for PSG.

A record-extending 13th French league title has already been sealed and there have been standout performances in the Champions League.

After struggling early on in the tournament, wins against Manchester City and Liverpool have underlined PSG's progress under Luis Enrique this season, with an exciting young team that is full of flair.

While less reliant on the individual brilliance of long-time talisman Mbappe, PSG has been driven by the outstanding form of Ousmane Dembele, who is realising the potential that convinced Barcelona to pay $272 million when signing him from Dortmund in 2017.

A run of 24 goals in 18 games between December and March established him as one of the deadliest forwards in Europe.

Leading 3-1 against Aston Villa after the first leg of their quarter-final, PSG looks in control, but has so often failed to live up to expectations in this competition.

Dark horse

Inter Milan leads Bayern Munich 2-1 in the closest match of the quarter-finals.

Davide Frattesi's 88th minute winner in Munich gave the 2023 finalist the advantage heading into the second leg at the San Siro.

Bayern, under Vincent Kompany, cruised to the quarter-finals and looks like regaining the German league title this season.

Inter could be the dark horse of this year's competition, having come so close to stopping City's treble of trophies two years ago.