The Norway international has been linked with a summer move to several clubs, including Barca.
Ter Stegen told Sport1: "His style of play and his willingness to score is impressive. When you see videos of him running from back to front at full speed and pushing the envelope with all his might, it's quite astonishing. It is pure will. Either you have this will or you don't. Haaland would make any team in the world better.
"But that doesn't mean he won't stay in Dortmund. BVB is a very well run club where they have done a great job in recent years. Why couldn't he stay there for another year? It would not be a step back at all.
"If he leaves, his new team will have one hell of a striker for the next ten years. I don't want to influence these matters as a player. We are not responsible for recruiting. We have a great team every year. At the end of the day, it's up to us to decide what to do with it."