Ten Hag wants them to build on Friday's opening night win against Fulham.
He told MUTV: "We have to improve and there are elements that should be better. We get a good review of the game and we took some problems out.
"We worked across the week on those problems, gave them solutions but also focused on our strengths. To even build further on those strengths.
"Most important is that we have the right team spirit. When I talk about the team, it's not about 11 starters. We need 16 players and to be ready. So we will name the squad and, from those 20, we need 16 players to do the job and win the game."
On the squad having a meal together midweek, Ten Hag also said: "It's good that they go together and have this meal but, finally, it has to result in togetherness on the pitch.
"So, yeah, they have to fight for each other. Football really is a team sport. It's about collaboration and, if you know the person, you are willing to do more for him. And it's about having the mentality, to compete shoulder to shoulder, fight for every inch; inch by inch. That is the right mentality and, when you can create this vibe, you can be a team that is very successful.
"That is what we are aiming for this season."