Real Madrid's interest crystallised on Friday evening, when the club made their first formal offer to Chelsea for the Spain international, who is preparing for his country's tournament opener against Cape Verde. The fee being discussed stood at €55m in guaranteed payments, with a further €5m in variables, equivalent to roughly £47.5m plus £4.3m in add-ons.
According to reporting from Spanish outlet Marca, the message that set the operation in motion came directly from Mourinho to Real Madrid's sporting department: Cucurella or nobody. With that instruction, the club moved quickly to open talks with Chelsea over personal terms, contract length and the structure of the fee.
Saturday became the day of detail, as the figures, contract years and variable clauses were worked through between the two clubs. With talks progressing but the player's final approval still needed, Mourinho himself picked up the phone.
The Real Madrid head coach called Cucurella directly, telling him he wanted the defender as part of his project and that there was no alternative in his mind.
"I want you in my project, it's you or nobody."
Cucurella, speaking with Spain's coaching staff in Chattanooga before the move to Atlanta, gave his approval following what was described as a relaxed conversation with the man who will become his new manager.
With all parties satisfied, the agreement was formally concluded on Sunday, an operation that took less than 48 hours from Real Madrid's first offer to the signing of the contract.
The timing created an unusual situation within the Spanish camp. News of the agreement broke from London at almost the exact moment Cucurella was completing his final training session with Spain before the World Cup opener, catching team-mates and staff off guard given how discreetly the operation had been handled.
Real Madrid are expected to make the move official on Monday morning, ahead of Spain's opening match.
Spain head coach Luis de la Fuente offered his reaction to the news, making clear the national team had no concerns about the timing affecting the squad's focus.
"We will be happy with situations that make the players happy. It doesn't create an uncomfortable situation. Nobody would do anything that could affect the group. We are pleased. It is good news and we celebrate it."
The transfer places Cucurella among the most lucrative figures in Spanish football in terms of fees generated across his career, with the move taking his cumulative transfer value beyond €150m once the figures from his moves through Barcelona, Getafe, Brighton and Chelsea are added together. For Real Madrid, the swift and decisive nature of the deal reflects the influence Mourinho already wields at the Santiago Bernabeu, just days into his second spell in charge.