Arsenal, Atlético Madrid, Bayern Munich, and defending champions PSG have lined up in the semi-finals of this year's Champions League after exhilarating quarter-final doubleheaders, which produced not just goals but one particularly shocking result.

There are not many questions over the progression of Arsenal and Bayern Munich, who have been the best teams since the start of the league phase, combining for just one defeat, which was inflicted by one on the other.

PSG, just as they did last season, started slowly and finished outside the top eight, but have picked themselves up in sensational fashion in the knockouts, while Atletico Madrid have repeated history against Barcelona.

From the clashes where the goals were flowing to the defensive masterclasses, we explore how the best four teams have secured their semi-final slots, even though La Liga giants did not fail to display their disciplinary struggles.

Arsenal set a new club record with semis berth

Arsenal reached their fourth Champions League semi-finals and for the first time in back-to-back seasons after a goalless draw with Sporting CP at the Emirates Stadium on Wednesday night to seal a 1-0 aggregate win.

At a time when the Premier League leaders are not performing at their best, especially in attack, the defence came to their rescue over the two legs, more importantly in Lisbon last week.

A Sporting CP team that had not lost a home game since August, winning 19 out of 20, could not find a way past a resolute Arsenal defence, and when it appeared the game was headed for a stalemate, Kai Havertz produced the match-winner.

That goal proved vital as it ended up deciding the tie as the Gunners, in the absence of the likes of Bukayo Saka, Martin Ødegaard, Jurrien Timber, and with half-fit Eberechi Eze, struggled for creativity.

Nevertheless, their defense was enough to power them into the semi-final as they kept their eighth clean sheet in 12 Champions League games this season, with David Raya equaling a club record held by Jens Lehmann since 2005-06.

Arsenal's victory in Lisbon was also their first away win over a Portuguese team in a European knockout game, ending a run of eight winless, but they have to improve in the final third if they are to win their first-ever Champions League title.

Bayern Munich ends Real Madrid's drought

After failing to win any of their previous nine meetings with Real Madrid, Bayern Munich snapped that run by winning both legs of their thrilling quarter-final clashes and sealing a 6-4 aggregate win to continue their remarkable season.

After winning the first leg away in Madrid, Bayern ended their barren run against Los Blancos, but even then, they would know that the tie was not over, especially after Arda Guler scored 24 seconds into the second leg to even the tie on aggregate.

But they continued to do what they do best by dominating possession, and found their way back into the tie every time Real Madrid scored in the second leg.

Alekandar Pavlovic leveled the score before Guler scored again via a sensational free-kick to become only the third Real Madrid player to score two goals from outside the box in a Champions League knockout match after Roberto Carlos and Cristiano Ronaldo.

Harry Kane grabbed his 50th Champions League goal to level the tie on the night before Kylian Mbappé grabbed his 70th in the competition and his 15th this season to join a list of just four players to score 15+ goals in a single edition.

Real Madrid had not lost a Champions League knockout game when leading at halftime since vs Galatasaray in 2013 while Bayern had not won a knockout game when trailing at halftime in the competition since against Arsenal in 2017, but their fortunes were changed in the second half.

Eduardo Camavinga's late red card for two bookings after coming off the bench in the second half proved costly, as Luis Diaz and Michael Olise scored two late goals after that incident to knock out Madrid.

Atlético extended perfect run over Barcelona 

Another evenly contested quarter-final tie ended with Atlético Madrid extending their perfect qualification record against Barcelona in the Champions League, all thanks to their first win in Camp Nou in two decades.

For Diego Simeone, that 2-0 first-leg result away from home have their work cut short, with the goals coming from Julian Alvarez and Alexander Sorloth after Pau Cubarsi's red card in the first half.

Notwithstanding, even as they threatened a comeback in the second leg, Barcelona have failed to learn the lesson that they got a bigger chance of progressing when they have none of their players sent off.

Their vulnerability was again exploited by Atlético despite going 2-0 up to even the aggregate scoreline in the opening 24 minutes at the Wanda Metropolitano thanks to goals from Lamine Yamal and Ferran Torres.

Atlético Madrid took advantage of the high line to score a perfect counterattack goal through Ademola Lookman just after the half-hour, making Barcelona the first-ever Spanish team to fail to keep a clean sheet in 15 consecutive Champions League games.

It was also their 44th goal conceded in the competition since the start of last season, the most of any team in that period, while Ademola Lookman moves into the top three Nigerians with the most goals in Champions League history.

Barcelona couldn't find another goal as Ferran Torres' second-half strike was rightly ruled out for offside before Eric Garcia was sent off for a last-man foul on Sorloth, leaving Barcelona down to 10 men for the final 10 minutes plus added time.

The victory on the night, although it was not enough to prevent their elimination, did make Barcelona the first team to beat Atlético Madrid at home in a Champions League knockout game since 1997.

Even though they were dominant in possession, Hansi Flick's team didn't show the discipline and clinical level demanded at this stage of the competition, and they can only have themselves to blame for falling short.

PSG just too good for Liverpool 

Even though they finished outside the top eight, PSG were the favourite heading into their quarter-final doubleheader with Liverpool, who have struggled for consistency this season and were always a tough draw away from exiting the competition.

After seeing off all four English opponents in as many knockout meetings recently, the French champions did not have much trouble adding Arne Slot's team to the list for a second season running.

They completed the double over the six-time Champions League winners with a 4-0 aggregate win after establishing a first-leg advantage in a dominant performance at the Parc des Princes.

Liverpool showed better resilience in the second leg at Anfield but could not break the PSG defence, and it was the visitors who secured a result needed by the host thanks to Ousmane Dembele's second-half brace to kill off the tie.

Desire Doue and Khvicha Kvaratskhelia scored the first-leg goals as PSG now reach the Champions League semi-finals for the third straight year, never missing out since the appointment of Luis Enrique in 2023.

They'll face Bayern Munich in the semi-finals in what will be a rematch of their league phase clash, just like the other semi-final between Arsenal and Atlético Madrid.

Semi-final Matchups 

Bayern Munich vs PSG

A fixture that has been played in the competition this season, Bayern Munich and PSG will clash for the third and fourth times since the start of the summer Club World Cup in America.

While PSG won their meeting in that tournament by 2-0, Bayern Munich has won their most recent meeting in the league phase, although Les Parisiens had a lot of regular players unavailable for that match.

Two of the most exciting teams in Europe, both closing in on their respective league titles, the rest enjoyed by PSG due to their postponed games have helped their cause, but Bayern could also have that leverage for this tie.

The Bavarians will become Bundesliga champions elect with a victory over Stuttgart this weekend, so Vincent Kompany can choose to give his best players minutes off to have them fresh for the semifinal doubleheader.

Arsenal vs Atlético Madrid 

The last time Arsenal and Atlético Madrid faced in a European knockout tie was in the 2017-18 Europa League semi-final, when the Spanish club progressed and went on to claim the trophy in the final.

Interestingly, that year, Diego Simeone's team went on to beat a French team, Olympique Marseille, in the final, and they may have a chance to repeat that run, with the possibility of facing a French team in this final, too.

However, they were completely outclassed in their only meeting with Mikel Arteta's Arsenal in the league phase, where the Gunners won 4-0 thanks to second-half goals from Gabriel, Martinelli, and a Viktor Gyokeres' double.

Arsenal also boasts a perfect record against Spanish teams under Mikel Arteta in this competition, winning all six games, including a double over Atlético's city rivals Real, in the quarter-finals last season.

Conclusion 

PSG have shown they are masters in all aspects by keeping clean sheets in their last three Champions League games, although they are not fancied to go through Bayern Munich without conceding, it promises to be an interesting tie.

On the other hand, Atleti against Arsenal is a completely different kind of matchup, but you can never rule out excitement, especially with Atleti the third-best scoring team in the competition, while they've also let in four against Arsenal not long ago.

The best teams have assembled in the semi-finals and in the four games to come, fans can expect the thriller and the unpredictable, because these four teams have shown they have what it takes to achieve climax finish, doing it in their own way.