Now with Kylian Mbappé everyone is wondering how two superstars will play together. They both have amazing talent and ambition. Reports say they respect each other and want to win together but there are concerns aboutthey can both score and create goals without hurting team overall balance. New season will show if these two great players and rest of team can work well together as strong unit.
Both Mbappe and Vinicius are biggest star players in coming years and they will also have to compete directly with each other for individual awards like Ballon d'Or or FIFA The Best. It undoubtedly will trigger conflict of interests between them while they are playing in a same club. It's more challenging for Real Madrid and Xabi Alonso as those players have very similar favorite positions and space on field so it's hard for them to both have their best playing conditions and maximize their performances for Real Madrid.
I don't know how Alonso will control or strengthen the defense with the attacking players. Every match has a plan and if the match manager can't replace those players in the right places then the strategies won't work. The strikers in the team should be desperate and focused on scoring goals. If they are busy defending to save goals then it will be detrimental to a team. For a strong team like Real Madrid, each player should play their own role and should be managed with big changes according to the team's needs but players who are used to playing in their positions should be deployed there. Every day is important for Alonso because he has taken charge of a team where he has to make more careful decisions and be ready to listen to criticism.
Maintaining balance between attack and defense is important with every team in football and Real Madrid had their big lesson in the past after selling Claude Makelele to Chelsea. After that big decision, they still had many attacking players in their club but no longer had good balance between attack and defense, hence they failed severely.
The transfer of Mbappe, before it happened, was skeptically warned by many people that it can potentially cause internal conflicts among star players in Real Madrid - it actually happened, and results in severe imbalance - that also occured in the last season. Xabi Alonso can not let Vinicius or Mbappe going away but he will have to solve very big challenging math in player resource and tactics in order to help Real Madrid playing more balancing as it is mandatory to build up a stronger and more competitive squad to win titles.