Some people described Mourinho as a perfectionist obsessed with detail.
That was true, although not quite in the way they usually meant.
He was meticulous rather than neurotic, the kind of manager who wanted every contingency considered before the match began.
Messi's introduction was a perfect example.
Before travelling to Madrid, Mourinho and The Lab had discussed the physical profile of Real Madrid's squad, the likely tempo of the match and the point at which fatigue would begin to become significant.
Their estimate had centred on the 70th minute.
So when the clock reached seventy, Mourinho made his move.
Messi had already been warming up.
The moment Mourinho beckoned, the seventeen-year-old hurried towards him.
The Portuguese leaned in, speaking close to his ear while repeatedly pointing towards different areas of the pitch.
Messi listened carefully and nodded.
The television cameras caught the entire exchange during a break in play.
"It looks as though Mourinho is finally going to change something," the commentator said. "He clearly isn't satisfied with the situation as it stands."
"And if Messi is coming on, you would imagine this is intended to add another attacking threat."
"The question is, who comes off?"
The match had remained finely balanced.
New Manchester United had spent much of the evening defending in a compact shape while Real Madrid controlled more of the ball.
But twenty-five minutes into the second half, the home side's intensity had begun to fall.
Del Bosque could see it too.
Several of his most important players were well into their thirties, and the pace Mourinho had imposed on the match was beginning to take its toll.
Del Bosque appeared ready to make a change himself.
Then he saw Messi preparing to enter.
He waited.
He wanted to see Mourinho's move first.
The fourth official raised the board.
Mikel was coming off.
The commentator sounded surprised.
"John Obi Mikel."
"That is aggressive."
"Mikel has played very well tonight, particularly in front of the defence."
Redondo smiled.
"Then Mourinho is not settling for a 1-0 defeat."
He glanced towards the pitch.
"He waited because he wanted these final twenty minutes."
Camacho did not smile.
He had begun to understand what Mourinho had been doing from the opening whistle.
Real Madrid's age profile made uncomfortable reading in a match played at this tempo.
Ronaldo Nazário was twenty-nine, but stamina had never been his greatest strength.
Zidane was thirty-three.
Figo was thirty-three.
Makélélé was thirty-two.
Roberto Carlos was thirty-two.
Juninho Paulista was thirty.
Salgado was thirty.
More than half the starting eleven were thirty or older.
Experience was an enormous advantage in European football.
So was composure.
But age also brought unavoidable consequences.
Recovery became harder.
Repeated sprints became more expensive.
Concentration declined more quickly under physical fatigue.
And when the tempo remained high for seventy minutes, even the most gifted players could no longer move with the same sharpness.
Spanish newspapers had already begun highlighting the pattern.
Real Madrid had been one of La Liga's best first-half teams all season.
Their second-half performances were far less convincing.
That did not necessarily mean anything by itself, but the broader trend was difficult to ignore.
Madrid often began matches with greater control than they finished them.
The warning had been obvious against Bayern.
They had led comfortably at the Bernabéu before conceding twice late in the match and nearly giving the tie away.
Florentino and the board were not blind to the problem.
That was why younger players were being promoted.
It was why Juan Mata had been given opportunities.
It was why the club had moved for David Silva.
But younger players took time to mature.
They could not replace an entire generation overnight.
Camacho looked towards Mourinho and felt increasingly uneasy.
He now understood the purpose of the earlier tempo.
New Manchester United had not merely been defending.
They had been making Real Madrid run.
And now Mourinho was removing a defensive midfielder and introducing Messi.
The shape changed immediately.
New Manchester United returned to their familiar 4-2-3-1.
Drogba stayed central.
Ronaldo moved to the left.
Messi took the right.
Kaká moved into the number-ten role.
Beckham and De Rossi formed the double pivot behind them.
The effect was immediate.
De Rossi won possession in midfield and fed Maicon on the right.
The Brazilian accelerated forward and released the ball into the space behind Roberto Carlos before the left-back could recover.
Messi had already started his run.
He stayed onside.
One touch took him towards the byline.
Then came a hard, low cross.
Drogba attacked the six-yard box.
Samuel got there first and headed clear.
Real Madrid survived.
But New Manchester United kept possession.
Within seconds, they came again from the opposite flank.
The warning was obvious.
Mourinho had removed one layer of protection.
In return, he now had two genuine wide attackers and two full-backs pushing forward against a Real Madrid side whose attacking stars were contributing less and less defensively.
The numerical balance on the flanks shifted instantly.
Figo was no longer tracking with the same intensity.
Zidane was tiring.
Ronaldo Nazário offered almost nothing defensively.
Roberto Carlos and Salgado were increasingly exposed.
Four minutes after the substitution, New Manchester United equalised.
Beckham controlled possession centrally.
He looked right.
Roberto Carlos had pushed too high and had not recovered.
Beckham sent the ball diagonally into the space behind him.
Messi was already moving.
The Argentine collected in stride and drove into the penalty area.
Helguera came across.
Messi slowed just enough to freeze him.
A shoulder feint.
One touch inside.
Then a composed finish beyond Casillas.
1-1.
The Bernabéu fell silent.
New Manchester United's bench exploded.
The move had taken only seconds.
Madrid lost possession.
Beckham released the ball.
Messi attacked the space.
Goal.
By the time several Real Madrid players had turned to recover, the ball was already in the net.
The equaliser transformed the match.
New Manchester United's confidence surged.
Mourinho waved them forward.
Madrid suddenly looked vulnerable.
Four minutes later, they were behind.
Ronaldo dropped deeper on the left and pressed Figo aggressively.
The Portuguese winger tried to protect the ball.
Ronaldo stole it.
He found Kaká.
Kaká returned the pass first time.
Ronaldo accelerated beyond Salgado and drove towards the left edge of the area.
Drogba attacked the centre.
Samuel went with him.
Ronaldo whipped the ball across goal.
Neither Drogba nor Samuel reached it.
Messi did.
He appeared at the far post and finished from close range.
1-2.
Two goals in less than five minutes.
The Bernabéu could barely comprehend what had happened.
For seventy minutes, the match had been tightly controlled.
Then Mourinho changed the structure.
Suddenly Real Madrid were being attacked at full speed from both sides.
Del Bosque reacted at once.
Ronaldo Nazário came off.
Morientes replaced him.
The Brazilian had scored Madrid's goal, but otherwise had struggled to influence the match.
Had Real Madrid won 1-0, the goal alone might have been enough to make him the hero.
At 1-2, the rest of his performance looked very different.
Ronaldo was clearly unhappy.
He walked straight past Morientes without acknowledging him, offered Del Bosque no greeting and disappeared down the tunnel.
Florentino, sitting beside Ethan, watched with a dark expression.
It had not been Ronaldo's evening.
Morientes immediately changed the feel of Madrid's attack.
He worked harder without the ball.
He challenged the centre-backs.
He attacked crosses aggressively.
And almost immediately, Real Madrid created something.
Juninho Paulista won a free-kick in an advanced area.
He delivered it into the box.
Morientes climbed above Terry and headed across goal.
Raúl had already anticipated the second ball.
He arrived in exactly the right place.
Header.
Goal.
2-2.
The Bernabéu came alive again.
Now there was no control left.
No patience.
No cautious positioning.
The match had become an exchange of punches.
Mourinho made no attempt to slow it down.
He wanted another goal.
He kept signalling his players forward.
Real Madrid responded in kind.
In the 83rd minute, Makélélé dispossessed Evra and found Juninho Paulista.
The Brazilian immediately switched play towards the right.
Figo received.
One touch to settle.
Then a cross.
Morientes attacked it.
Header towards goal.
Čech reacted sharply and punched clear.
The ball dropped outside the penalty area.
Zidane had already read the rebound.
He controlled it with his chest.
Then struck.
The shot flew like a missile.
Čech dived.
He got fingertips to it.
Not enough.
3-2.
The Bernabéu erupted again.
Del Bosque had his lead back.
This time he decided to protect it.
The tiring Figo came off.
Roberto Carlos followed.
Raúl Bravo and Pavón were introduced to reinforce the defensive structure.
The reaction from sections of the crowd was immediate.
Boos.
For many Real Madrid supporters, defending a one-goal lead at home felt beneath the club's identity.
They wanted another attack.
Another goal.
They wanted New Manchester United finished.
Mourinho did not share their concern for aesthetics.
De Rossi was beginning to cramp.
Michael Johnson replaced him.
The message remained unchanged.
Keep attacking.
New Manchester United continued to press.
The decisive moment came in the 89th minute.
Kaká received centrally.
Juninho Paulista tried to stay with him.
Kaká powered away.
He carried the ball towards the edge of the penalty area and looked as though he might shoot.
Instead, he slipped a diagonal pass into the space on the right.
Messi had timed the run perfectly.
Casillas came out.
Messi arrived first.
One touch.
Finish.
3-3.
Hat-trick.
For a moment, the Bernabéu was stunned.
Then came a wall of noise.
Some of it disbelief.
Some anger.
Much of it directed towards Del Bosque.
The supporters who had booed his defensive substitutions now had their evidence.
At least in their minds.
Madrid had tried to protect the lead.
Madrid had conceded.
The conclusion seemed obvious to them.
Mourinho still wanted more.
He urged New Manchester United forward even after the equaliser.
But Madrid's substitutes finally stabilised the defence.
Raúl Bravo made an important interception.
Pavón won a crucial aerial duel.
Casillas dealt with one final cross.
The referee blew for full-time.
Real Madrid 3-3 New Manchester United.
Six goals.
Five of them in the final twenty minutes.
What had begun as a tense European semi-final had ended as an extraordinary attacking contest.
The Bernabéu continued to whistle after the final whistle.
Del Bosque was the main target.
Many supporters believed his late caution had allowed New Manchester United back into the game.
The criticism was ruthless.
Only a year earlier, Del Bosque's adjustments had helped Real Madrid win the Champions League.
He had delivered major trophies consistently.
Now one disappointing result was enough for sections of the Bernabéu to turn on him.
Ethan listened to the noise and shook his head.
Football supporters had short memories.
Real Madrid supporters could sometimes have even shorter ones.
People often appreciated stability only after losing it.
In Ethan's previous life, Madrid had spent years looking backwards, romanticising former managers after they were gone while attacking whoever currently occupied the bench.
One coach would be blamed for lacking authority.
The next for lacking attacking football.
Another for failing to control the dressing room.
Then supporters would wait for the next supposed saviour.
The cycle rarely stopped.
The problem was not always the manager.
Sometimes the institution itself made sustained success almost impossible.
Ethan had always believed that if a club demanded perfection every week while undermining anyone who failed to provide it, eventually even the strongest coach would be swallowed by the environment.
No manager, however brilliant, could build indefinitely inside permanent instability.
Not even someone as forceful as Mourinho.
At the Bernabéu, New Manchester United had just seen both sides of Real Madrid.
The brilliance that allowed their superstars to score from almost nothing.
And the pressure that turned a 3-3 draw in a Champions League semi-final into an occasion for boos.
That contradiction was part of what made Madrid extraordinary.
It was also part of what made them vulnerable.
(To be continued.)