Los Blancos opted to bring their former boss back to the Spanish capital earlier this summer following two trophyless seasons under a combination of Carlo Ancelotti, Xabi Alonso and Alvaro Arbeloa.
Mourinho has already looked to put his stamp on preseason, with a rigorous physical programme, despite several star names still missing after the 2026 FIFA World Cup.
Kylian Mbappe, Jude Bellingham and new signing Marc Cucurella have not featured at all up to this point and Mourinho has revealed his concern over Bernardo Silva's summer condition.
Despite his comments on Silva and the likelihood of not being at full power until at least mid-September, Mourinho will not be bringing in too many extra faces, as he plans for a key year in Madrid.
"We want a small squad. I’d say around 20 players, plus those unlucky enough to be out with injuries.
"Militao, Mendy and Rodrygo are players I don't expect to have back in the coming weeks. So, we also need players like Bernardo, who can play in different positions."