Saints and United meet on Monday night.
Hasenhuttl said, "In the beginning, people did not underestimate him as he had a very good start and was winning all the games. Then it was the opposite.
“Now it's a little bit special for everyone around the world to see what he's doing and that's a problem in our business.
“It's more important that he is convinced about what he is doing and at the moment he is proving all the experts wrong.
“The signing in the winter has helped them massively. That is clear. The team is completely reorganised and very different, but still the big challenges are to come.
“With such a club, it's always important that you don't just have a good 100 metre record but one for the marathon.
“To be successful with such a club you have to develop the team and game every day over the whole season – you can never stop learning and improving.
“And never stop winning because winning is normal and losing is always a disaster so that's the challenge with these sort of clubs. Right now, he's doing a good job in that respect."