As of July 1, Mbappe is officially going to be a Real Madrid player.

I'm very excited about him despite there are still nearly 2 months to go for new season to start.
From now on I really don't know who can stop this team in the La Liga. Normally we would say Barcelona as the biggest candidate. However they lack the strength for doing that. Laporta is also aware of the huge threat now but he can't do anything unless Barcelona finds a lot of money from somewhere. Maybe they can make some money by player sales but I don't know whether they intend to give up on any of their decent players.
Frenkie de Jong has been on the rumours to be sold but it is hard to be sure of it. He is a great player who is quite injury-prone at the same time.
