Last season was a struggle for United, which saw manager Ole Gunnar Solskjaer shown the door by November and then witnessed interim successor Ralf Rangnick also flounder, with United finishing sixth in a humiliating end to a forgettable campaign.
Sunday's encounter against Brighton will therefore be significant for new boss Ten Hag in his first competitive match in charge after an intense pre-season that included big wins over Liverpool and Crystal Palace.
However, that does not mean it is all smooth sailing at United. Cristiano Ronaldo did not take part in the pre-season tour of Thailand and Australia due to personal reasons amid reports he wants to quit the club.
However, he did play against Rayo Vallecano and was on Sunday named on the bench for the season opener.
The mood, however, remains optimistic in the dressing room.
"I think definitely for the team we're moving in the right direction," United defender Luke Shaw told MUTV.
"The manager obviously had to come in and bring in his ideas, his structure, what he wants from the team - as a team and also individuals.
"I think everyone's sort of buying into that and really enjoyed pre-season.
"Like I said, we've definitely moved in the right direction but we've also got a lot to improve on. We know that, we know we need to get better."