The Red Devils boss has Paul Pogba, Nemanja Matic, Ander Herrera, Marouane Fellaini and new signing Fred to call upon in the middle of the park.
Despite that, though, it appears Mourinho wants more.
United have been heavily linked with Lazio star Sergej Milinkovic-Savic, while Toni Kroos has also emerged as a target.
But Transfermarketweb say their sole focus is Modric - and they have one reason to believe a deal can be struck.
It is claimed Real will offer the player a new deal.
Luka Modric: Croatia and Real Madrid star has played under Man Utd boss Mourinho before (Image: GETTY)
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Modric and Rakitic react to Ronaldo Juventus rumours
But that will only be until 2020 and Modric, who feels he can play at the top level for many more years, may want a longer contract.
That is where United can intervene.
However, whether Real allow another key asset to leave the club remains to be seen.
Cristiano Ronaldo has left for Juventus and question marks remain over Gareth Bale, who is also a United target.
Relations between the clubs are also strained with Real refusing to let Alvaro Morata join United last summer.