We were served up an all-timer of a game at the Parc des Princes last week, and the second leg promises more of the same. For Paris Saint-Germain and Bayern Munich, the 2025-26 season will be measured by the Champions League. The contest resumes at the Allianz Arena on Wednesday, with PSG holding a one-goal lead.

Twenty-four hours after the fireworks in Paris came a different sort of game. Diego Simeone’s Atletico Madrid and Mikel Arteta’s Arsenal, two coaches who have built reputations on defensive identity, played out a tense, attritional first leg that finished 1-1.

Two ties, two shades of intensity. A reminder that the same sport can grip you in entirely different ways. The second legs will decide who walks out at the Puskas Arena in Budapest on May 30. But who will be in the final? Here are the numbers and trends that may give us a clue…

Arsenal v Atletico Madrid (agg 1-1)

Diego Simeone has rarely walked into a Champions League knockout against a side more defensively drilled than his own. Under Mikel Arteta in the European competition, Arsenal concede just 0.65 goals per game across his 37 matches in charge, the lowest ratio of any manager in the competition’s history with 20-plus games. Atletico, on the other hand, have evolved. They have scored 35 goals in this Champions League, their highest in a single edition, and arrive at the Emirates as the most attacking iteration of Simeone-ball we have seen.

At the Metropolitano, Atletico produced 2.22 expected goals. Only Aston Villa in December (2.52) have managed more against Arsenal in any competition this season. The threat ran through the strike partnership of Antoine Griezmann and Julian Alvarez, two forwards given the freedom to roam, with a chemistry that comes alive in transition. Alvarez alone accounted for 1.00 xG, more than any other player on the pitch. He scored his penalty, and now has 14 goal involvements (10 goals, four assists) in 14 Champions League games this season, making him the first Atletico player ever to reach double figures for goals in a single edition.

Gyokeres scored in the first leg and has 21 goals for Arsenal this season (Dan Mullan/Getty Images)

While Atletico’s strike partnership is symbiotic, intricate and cerebral, Arsenal have an explosive focal point in Viktor Gyokeres — a different model of striker entirely. He is an orthodox shoulder-runner, explosive and vertical in his movement: a wrecking ball among the finesse around him. In Madrid, he buried his penalty. Against Fulham at the weekend, he scored twice and added an assist, all in the first half. He now has 21 goals in his debut Arsenal season.

The contrast with Alvarez extends from profile to involvement, and it showed clearly in Madrid. Gyokeres had 15 touches. Alvarez had 49. The two strikers have two very different jobs. One pins the last line. The other drops deep to facilitate and dictate, weaving himself into the very fabric of Simeone’s build-up.

The first leg was defined by two contrasting halves. Atletico were under the cosh in the first, and Simeone used half-time to change both personnel and shape. He switched from a back four to a back three, with Robin Le Normand replacing Giuliano Simeone alongside David Hancko and Marc Pubill. The effect was almost immediate. Atleti drew level and seized control: possession climbed from 48 per cent to 55 per cent, and their xG rose from 0.22 in the first half to 1.99 in the second.

In the first half, Atleti’s midfield pairing of Koke and Johnny Cardoso was overrun by Arsenal. Declan Rice, as he has been throughout the season, was metronomic. His 83 passes, 12 line-breaking passes and 12 progressive carries were the most of any player on the pitch in all three categories.

The head-to-head reads in Arsenal’s favour. Atletico have shipped 16 goals in seven Champions League away games this season and lost six of their last seven away games against English sides. The 4-0 defeat at the Emirates in October is their joint-heaviest in continental history.

The new UEFA format rewards the top two league-phase finishers with the home leg in the semi-final. Tuesday will test whether Arsenal can convert that reward, at the same stage where they were knocked out last year.

Bayern Munich v Paris Saint-Germain (agg 4-5)

PSG take a one-goal lead to the Allianz Arena, and the precedent in two-legged ties favours the Parisians. Bayern have lost the first leg of a UEFA two-legged semi-final on 10 previous occasions and overturned the deficit only once — more than 40 years ago. They have lost their last five two-legged Champions League semi-finals. PSG, by contrast, have won 36 of their 43 previous UEFA two-legged ties when winning the first leg, and 14 of 17 when the lead was a single goal. An 82 per cent conversion rate.

The first leg was scintillating, and neither manager intends the second to be any different. Both Vincent Kompany and Luis Enrique have hinted, in their own ways, at more of the same.

What unfolded in Paris was not random. It was controlled chaos: a breathless exchange of punches across 90 minutes. Both teams pressed man-to-man with relentless intensity, and the game became a chain of one-on-one duels.

Michael Olise celebrates after scoring against Paris Saint-Germain in the first leg (Anne-Christine Poujoulat / AFP via Getty Images)

The only space was behind the defensive lines, so both teams played long passes at almost double their season average to exploit it. In midfield, Aleksandar Pavlovic and Joshua Kimmich played 24 line-breaking passes between them, more than PSG’s four midfielders managed combined (17, of which Vitinha contributed seven). It was the only time this season a midfield facing PSG has out-line-broken Vitinha.

Possession told the same story. PSG average 64 per cent possession in this Champions League, the highest of any side in the competition. In the first leg, though, they had just 43 per cent. PSG concede an average of 17 touches per game in their own box across this Champions League campaign. Against Bayern, they conceded 52. The xG read 3.06 to Bayern, 1.90 to PSG.

The underlying numbers suggest Bayern had the better game. PSG had five shots on target and scored five goals, a mark of exceptional finishing.

When the press creates one-on-ones, talent decides and the talent on the pitch was supreme. Bayern’s front three of Harry Kane, Michael Olise and Luis Diaz have hit 100 goals across all competitions this season, only the third trio since 2013-14 to reach the mark.

PSG’s three of Khvicha Kvaratskhelia, Desire Doue and Ousmane Dembele are arguably the most fluid attacking unit in Europe. They chop and change, switch flanks, drag defenders into empty space, and become impossible to defend against in full flight. Kvaratskhelia has been involved in 15 Champions League goals this season, a record by a PSG player in a single campaign.

Bayern have lost just one of their last 29 Champions League home games. They have won all six this season, and have averaged five goals per game across their last eight at the Allianz. The fortress is intact. Both sides also walk in fresh. PSG and Bayern rotated heavily over the weekend, with Luis Enrique resting almost his entire expected XI for Lorient, and Vincent Kompany doing the same against Heidenheim.