The combination of these two players in the attack will be a disaster to any club defense if they can play as one with a strong bond. Mbappe and Vini are irreplaceable and that was why Ancelotti went for Mbappe when he was in PSG. Alonso will work on them and make them play with humility so that they can put in their best performance when they are on the pitch.
If the two of them can play as part of a team, their duo will definitely be among the best and will be able to break through any team's defense and score goals. Kylian Mbappe in particular could be Alonso's biggest tool and he will definitely want to use that weapon and work on it more. Although Kylian Mbappe's list of personal achievements is a bit big, his list of team achievements is very small. He will have to give up his personal goals and fight for team achievements, then his list of personal achievements will be even bigger. Xabi Alonso might work on this issue more and force Mbappe to perform for the team.