Gagliardini playing tonight is a problem. But the bigger problem is, if we somehow win tonight, he will keep getting those minutes, and put us in problems in future games.
He basically makes us play with 10 men, and completely disassembles our midfield play.
Imagine the team as a building. If one of the columns or beams in a structure is seriously damaged, then the structural safety of that building becomes questionable (at best). Gagliardini is that damaged column in our team. And Conte the engineer ignores this danger.