Four teams, two knockout rounds and a final in Budapest on May 30. The 2025-26 Champions League reaches its decisive stretch with a semi-final draw in which the numbers have a clear opinion:Bayern Munich and Arsenal are the favourites to be in Hungary. But football, as Diego Simeone knows well, does not always obey models.

MARCA has developed a probabilistic model based on ClubElo's Elo ratings – the most rigorous rating system in European football, which weights each result according to the level of the opponent and the home team and based on more than one million matches since 1955 – with data updated on April 16, 2026. The result is a map of probabilities that goes beyond simply who is better. It incorporates home court advantage (+65 Elo points for playing at home), the historical rate of draws in the Champions League (27%) and the two-legged knockout model, with extra time and penalties at 50/50 in case of an aggregate equality.

From this, he assigns Bayern a 56.2% chance of qualifying against PSG, and Arsenal 72.3% against Atletico Madrid.

PSG - Bayern: the most even duel that the Allianz will resolve

Bayern (2021 rating) are just 47 points ahead of PSG (1974 rating), the smallest difference in the four European semi-finals to be played this week. In terms of probabilities of classification, the model assigns Germans 56.2% compared to 43.8% for Parisians. A statistical coin flip disguised as a duel between two of the most powerful clubs on the planet.

The key nuance is in the distribution of the matches. PSG play the first leg at home and that makes them slight favourites in the first half: 38.4% chance of victory for Luis Enrique's team compared to 34.6% for Bayern, with a 27% draw. In other words, in Paris there is no clear favorite. The balance is almost total.

The return, however, changes the scenario radically. At the Allianz Arena, Bayern are transformed: a 47.9% chance of victory for Vincent Kompany's side, compared to just 25.1% for PSG. Whoever arrives at the Allianz with something to defend will have a huge advantage; whoever manages to climb it, a mountain to climb.

The recent precedent does not help PSG. In the league phase of this same season, Bayern won at the Parc des Princes 1-2 with a brace from Luis Díaz. The French know that defeating the Germans in Europe is not easy. But they also know that they are defending champions, that their rating has grown by more than 30 points since October and that Luis Enrique knows no fear.

Atletico-Arsenal: Simeone needs a calculated miracle

The model is conclusive: Arsenal (rated 2050) is the strongest team in Europe right now, and the difference with Atlético de Madrid (rated 1862) is 188 points. To understand the magnitude of that gap, it is enough to know that in the quarter-finals Arsenal were ahead of Sporting CP by 196 points. In other words, Simeone's Atletico is, in the eyes of the model, almost at the level of the Portuguese team. But we must also remember that Sporting lost 1-0 on aggregate and that they were about to get the English in trouble.

The chances of qualifying assign Arsenal 72.3% compared to Atletico's 27.7%. But there is one fact that explains everything and that makes this tie something different from what it seems:Arsenal are favourites even playing at the Metropolitano. The first leg on Wednesday, April 29 in Madrid gives the Gunners a 48.9% chance of winning that match, compared to just 24.1% for Atletico. A draw – 27% – is the best ally of the red-and-white team in their own stadium.

That's Simeone's plan, although he would never call it that: to hold on at home, not lose, and bring the 'Gunners' to the Emirates alive. Because in the second leg, in north London on May 5, Arsenal becomes a machine: 59.2% chance of a home victory, only 13.3% for Atletico. If the Metropolitano ends in a draw or a victory for the Colchoneros, the semifinal becomes a different game.

The precedent of the quarter-finals adds to the red-and-white optimism: Atlético eliminated Barcelona – who were clear favourites, with a 62.1% probability according to the same model – thanks to an impeccable tactical performance in the two games. Simeone has already shown that he knows how to win European ties that he shouldn't win. The question is whether he can repeat it against the best team on the continent for Elo purposes.

What the model tells us and what it cannot say

Elo models measure the strength accumulated over months. They do not measure the form of the last week, the absences, the competitive hunger or the ability of a coach to prepare for a specific match. Arsenal have been the team with the highest rating in Europe for six months, but it is also true that in the Champions League they have suffered more than expected – they only beat Sporting 1-0 on aggregate – that they arrive with certain dues and that they accumulate a strong mental and physical wear and tear in their fight for the Premier League.

Meanwhile, Bayern have reached these semi-finals with an exhibition of power against Real Madrid (6-4 on aggregate) but also showing vulnerabilities. An irregular Madrid this season had him on the ropes. For their part, PSG look better every day and Atletico have shown that predictions do not go with them.