Italian journalist Tancredi Palmeri approached Mourinho as he left his pre-match press conference at Valdebebas on Monday and presented him with the sprinkler, wrapped in Inter's blue and black ribbon, as a nod to one of the most iconic scenes in Champions League history.
In 2010, Mourinho's Inter Milan lost the second leg of their semi-final 1-0 at Camp Nou but progressed 3-2 on aggregate to eliminate Pep Guardiola's Barcelona, with the celebrations of Mourinho and his players famously drenched by the stadium's sprinklers.
Speaking later that night on Radio MARCA's 'Otra Ronda', hosted by Carlos Vicente 'Chitu', Palmeri revealed the planning behind the gesture.
"It was planned. It's not that I normally have sprinklers at home, so I had to go looking for one. I also had to find the two black and blue ribbons in Inter's colours," he said, laughing. He acknowledged the gift broke with convention: "I know it's not the done thing, I know I overstepped."
Palmeri explained he had waited 16 years for Inter to meet Mourinho again in European competition, and that the gesture carried a deeply personal meaning beyond simple homage to a famous night.
"When Mourinho did what he did in that moment, it put a smile on the face of someone very close to me, who was going through the worst pain a parent can experience," he said.
He explained the win over Barcelona had briefly restored a smile to someone dealing with profound grief, and that he had long wanted to mark the moment with a tribute to Mourinho, though the right opportunity to explain it to him directly had never arisen. Asked what one gives to a man who already has everything money can buy, Palmeri said the sprinkler idea simply came to him as the fitting answer.
Beyond the gift, Palmeri also gave his assessment of Tuesday's fixture, suggesting Real Madrid's recent defeat makes them a dangerous opponent for Inter.
"The worst thing is facing a strong Mourinho team after an undeserved defeat," he said, before adding that in football "deserving or not deserving doesn't exist." He argued Madrid had shown real quality despite the loss and would arrive hungry for revenge.
"You could see they know how to play and they're hungry, so it's the worst possible situation for Inter," he said. "I wouldn't be surprised at all if Real Madrid's fury is unleashed tomorrow at the Bernabéu."
He noted Inter head into the match with some fatigue of their own following a win over Napoli, but argued a defeat in Madrid would not be catastrophic for the Italian side given the scale of the challenge.