The 24-year-old has gone four top-flight games without a goal
Armstrong earned his big-money move to the south coast after striking 28 times for Blackburn in the Sky Bet Championship last term.
The 24-year-old marked his Saints debut with a goal in the opening weekend defeat at Everton but has fired blanks in the four games since, with his new club still searching a first league win of the campaign ahead of Sunday’s clash with Wolves.
Hasenhuttl – who lost lethal striker Danny Ings to top-flight rivals Aston Villa in early August – is pleased with the overall impact of his summer signing and believes patience is required for him to become prolific at the higher level.
“We think he fits perfect in our shape, how we want to play football, and I’m very happy to have him here,” said Hasenhuttl.
“He’s a good lad, he’s very working hard, against the ball he has a lot of runs – negative runs, if you want, in the last game against Man City for us – and this is, vir my, for a striker a very important part.
“And it’s normal if you have to work so much against the ball that you are sometimes lacking of the few inches of the right position when you want to score.
“He has to adapt to the high intensity of the games then he will also make his goals in the Premier League, I’m sure.
“It’s a different level but he has shown that he has some skills that are definitely very, very helpful for our team.”
Volg die 3-1 defeat at Goodison Park on August 14, Southampton have registered four successive draws, including picking up creditable points against Manchester United and Manchester City.
Wolves, who appointed Bruno Lage as successor to Nuno Espirito Santo in June, travel to St Mary’s having come from behind to win on their two previous visits.
Hasenhuttl dismissed the importance of throwing away those leads and – despite recently losing the services of Ings, Ryan Bertrand and Jannik Vestergaard – believes he now has better strength in depth at his disposal.
“This was very disappointing for us but this is far away in the past and I think we need to focus on our situation at the moment,” he said of last season’s home defeat to Wolves.
“You only come to the situation where you can drop points in winning positions when you get into a winning position so we must have done something right in the beginning.
“What is different this season is definitely that we have more quality on the bench – we can definitely make changes a little bit earlier.
“And that gives me more alternatives for changing a game plan. Definitely we have in total more quality this season in the squad – you can see that in every session.
“We have a new squad, we have a good mentality, lots of young players who are pushing hard to play and give us their qualities on the pitch.
“It’s a pleasure for me to work with this team and hopefully we can be so strong that we find our first win.”