Not many teams will press them as aggressively as Brighton.
The United players obviously haven't fully absorbed the way ten Hag wants them to play yet and are having to take an extra second to think about what they're supposed to do.
Brighton are probably one of the worst sides in the country to play like that - we've all seen to how much they push our players after 5 years of Pep's coaching.
What's worrying for United is Brentford are not that far off Brighton, Liverpool are better and Southampton are pretty intense too, so it's going to be a tough start to the season for them.