I mean, he always performed in the CL though.

Not disagreeing with that. It is just that in a club like United with its current situation and the level of competition every other game is a big game - Slip up and goodbye to CL qualification as actually ended up being the case. That and the fact that there were no quality backups like Ceballos always meant that the move was high risk. Case should have picked a move like Inter, would have been perfect