With Thursday's Copa del Rey semi-final in mind, Diego Simeone decided to make alterations to his first choice XI in Bilbao and the experiment went horribly wrong. Both Falcao and Gabi were ineligible to play and El Cholo left Miranda and Koke, the hero of last week's win over Levante, on the subs' bench. Their replacements, Cata and Emre, were simply not up to the task. It was as though the entire team had digested his message that the important game is not this one but Thursday's clash with Sevilla in the Copa del Rey - an idea which isn't without its logic but the fans are still dreaming about winning the league and tonight's result has left them off the pace while their closest rivals Barcelona and Real Madrid both won.
That isn't to say that this wasn't an entertaining game - far from it. Those present in San Mamés, the Cathedral of football, witnessed a captivating encounter - one which lived up to its billing and was reminiscent of some of the legendary battles between these two classic sides of the Spanish game.
Bielsa's side took the game to the guests and if it wasn't for the excellent Courtois, the first half almost certainly would not have ended goalless. How the ball didn't enter in the opeing 45 minutes was a miracle.
Little by little, Aduriz, Muniain and De Marcos began to encroach on the Belgian's goal and it was only a question of time before the deadlock was broken. On 50 minutes, Athletic won a corner. Godin failed to pick up San José, leaving him free to plant a header past the keeper.
Courtois continued to keep Atleti in the game while Iraizoz prevented Raúl García from grabbing an equalizer at the opposite end. Simeone's troops were left reeling when Susaeta tucked the ball inside the post with little over 10 minutes of normal time remaining and they would have had few complaints about the winner - a magnificent build-up involving several players was crowned by De Marcos who rifled a majestic shot into the top corner. Athletic will feel that in some ways, they have got even for the Europa League defeat to the Madrileños in Bucharest while Simeone will be wondering if he made the right decision to make the Copa del Rey a priority.