Pre-season friendlies mean nothing other than fitness. I remember Chelsea losing 3-0 last season didn't they? Or the season past Lukaku looking like a world-beater only to be sent on loan, or Aspas bossing it for Liverpool only to have a disaster of a season.
It's good for youngsters to feel the weight of the shirt and show the manager they could play a part, but they have to be exceptional, much like that lad Pereira has been for United in their past 2 games. No wonder Juve and PSG were interested before he renewed his contract with them.
The one thing I always notice though is how Hazard always comes back looking chubby hehe. He's a bit like Gotze in that regard.