I am amazed, that anyone who have watched Weigl play could come up with the idea, that it would be great to purchase him to play in a Mourinho side. His skillset is completly the opposite of a holding midfielder for the style Mourinho prefers, that it is ridiculous.
1. Julian ist not strong. Although he is tall, his weight is just 72 Kilo. He has barely muscles to fend off attackers is relying solely on his positional play to defend. But within a system, which drops deep, your positioning gets less important, because it is unlikely you cant get into the space with a small sprint. Only in a system, where the holding Midfielder has to cover a lot of space, his greatest strength in defence comes to fruition.
2. His greatest strength is his technique, which is quite uncommon for a number 6. Again, this is quite useful even in a more counter attacking side, but is not nearly important. Because the a player in this position has a lot less time on the ball in a counter. But in a side with a slower build up he is the key player, because he initiates the attacks and is the player with the most actions on the ball. The opposition has more time to get in shape and is able to collectivly press higher up the pitch. Then you need a player who don't looses the ball in an dangerous area. But in the Permier League, there are only three teams who have a higher pressing (Tottenham, Liverpool and City).
So why you think Julian Weigl is the best player as a holding midfielder for United? Has Mourinho ever used a player like him to his maximum strength? His Holding midfielders in the past were guys like Essien, Matic, Cambiasso, Motta etc..
The only exception to that were Xabi Alonso, but he is a player most famous for his long balls, something Julian doesn't excels at. For that you could buy Sahin.
So in the end, buying Julian Weigl would be the next new shiny player, who dissapoints all United supporters. Many will say, that he is just not good enough, as if a specific skill set is useable to the same extent in every setup. This transfer "strategy" is the root of all the waste of a shitload of money in the past and it is worrying me for United, that so many fans don't get it. As if you all have become Galactico-Fans.