The Signal Iduna Park hummed with a nervous energy as the first half of the Champions League clash against Arsenal drew to a close.
The yellow wall was in full voice, a constant roar of support that seemed to shake the very foundations of the stadium, but the mood on the pitch and in the stands was tense. The score was tied at 1-1, a frantic, end-to-end affair that had seen both teams trade blows like heavyweight boxers in a title fight.
Mateo watched from the bench, a rare experience for him in recent weeks. The plush leather of the substitute's seat felt unfamiliar, a stark contrast to the adrenaline-fueled environment of the starting eleven.
Klopp, with a paternal arm around his shoulder before the match, had explained the decision with a mixture of tactical pragmatism and genuine concern. "You have played so much, for us, for Spain. Your body is still growing, still adapting. We must be smart, Mateo. Tonight, you are our secret weapon, our ace in the hole."
