Having completed the signing of Marc Cucurella from Chelsea, Mourinho also has deals for Ibrahima Konate, Bernardo Silva and Denzel Dumfries well advanced.
Replacing the 34-year-old Courtois will prove considerably more complicated, given his standing as one of the finest goalkeepers in the world.
According to journalist Miguel Serrano, Real Madrid's preferred profile for that eventual succession is Bart Verbruggen, the 23-year-old who has established himself as Brighton's number one goalkeeper.
Verbruggen's contract with Brighton runs until 2028, and Real Madrid are reportedly planning to pursue the move for the summer of 2027 rather than the current window.
Brighton, however, are keen to avoid the situation dragging on, and want clarity on Verbruggen's future sooner rather than later.
The Holland international's club also face competition from elsewhere for his signature. Both Paris Saint-Germain and Bayern Munich have shown interest in Verbruggen, with the German champions reportedly open to completing a transfer as early as this summer.
Verbruggen joined Brighton from Anderlecht and quickly became one of the most reliable young goalkeepers in the Premier League, catching the eye with his shot-stopping and composure with the ball at his feet.
His form has also made him a regular for the Netherlands, where he has established himself as the national team's first-choice goalkeeper at a remarkably young age.
Real Madrid's situation with Courtois is complicated by the Belgian's status as one of the club's most important players over the past several seasons, making any succession plan a delicate balancing act.
The club do not currently trust understudy Andriy Lunin to be Courtois' long-term heir, which has prompted the search for fresh options including Verbruggen and Borussia Dortmund's Gregor Kobel.
Real Madrid's interest in Verbruggen reflects a broader pattern under the club's recruitment strategy of identifying younger talent early, even when there is no immediate vacancy to fill.
Whether Verbruggen would be willing to leave a starting role at Brighton for a backup position in Madrid, even with the promise of eventually inheriting the gloves, remains an open question that will likely shape how this saga develops.
For now, Real Madrid will continue to monitor the situation, while Brighton wait to see whether the Spanish giants are prepared to make their interest concrete before other suitors move first.