It seems that Xabi is not satisfied with the players he currently has. Especially the current condition of the center players because they were left behind by Beligham who had shoulder surgery. Xabi still sees many shortcomings in his young players. I think this makes a lot of rumors he still wants to buy a midfielder. One of his targets is Man City midfielder Rodri. Real Madrid are ready to bid £100 million to sign the Manchester City star. Although Rodri's condition last season rested a lot due to injury and made Man City not get good achievements.
Source:
https://www.thesun.co.uk/sport/35984346/real-madrid-transfer-rodri-man-city-offer/After what the team experienced when they played against PSG in the club world cup, I saw that coming, if you noticed the Midfield was mostly dominated by PSG in that match which gave them the opportunity to control possession mostly and create chances, therefore he doesn't want that to repeat again in the future that's why he's calling for more transfers especially in that area, if Perez would agree to his demands I think they'll go for someone that's more experienced, someone that would comfortably replace Modric but I wonder who they'll go for, no big club would release their top players except Madrid give them an offer they can't reject.