The Red Devils head to St Mary's Stadium out to extend their winning streak to eight straight league victories on the road, stretching back to 'Project Restart' last summer.
Hasenhuttl's well-drilled side, though, bring an impressive record of their own into Sunday's match, unbeaten in the last seven games which put them into the top six.
Hasenhuttl, however, knows Southampton must bring their own best form, no matter which United might turn up come kick-off.
"If they would have more consistent, high performances, then they would be top of the table," the Southampton boss said.
"They are not at the moment and the reason for that is they have not had such a high performance every week - and you never know what you are going to get.
"On some days they are amazing and on some days they are struggling, so it is about how much of an issue we give them with our way which we play.
"That is the reason why we try always to concentrate on what we are doing.
"If we do well, if we do every part of the game in a way we can do, in a nasty way for every opponent, then we have a chance to take something.
"But in such games you need everything - you need the luck at the right moment, a clinical finish, don't give too many chances away, because they will score otherwise, and the rest is about fighting for everything."
Despite his own side's impressive current form, Hasenhuttl knows the hard work must continue.
Southampton celebrate scoring
(POOL/AFP via Getty Images)
"In the last weeks, we have seen some good progress in our game," the Austrian said.
"Still now it is not getting easy winning games in the future. It is getting more and more difficult because opponents will watch us and analyse us.
"They will find solutions to play against us and that means we have to get better. Every week to do some things better and learn how to play every part of our game the best we can do."
Southampton have progressed under Hasenhuttl, who took over during December 2018 with the club fighting to stay in the Premier League and last October saw his side thrashed 9-0 at home by Leicester.
The former RB Leipzig boss accepts life is "more enjoyable" at the moment, but will continue in the same mindset as when the outlook was rather less positive.
"As a manager, you are more necessary for a team when it is not running (well), when it is not working because they look at you much more then," Hasenhuttl said.
"You are there to find solutions, to solve the issues and this is different to now.
"Now, they are also looking at you and listening to what you tell them, speaking about a different level, looking at the small details we can still improve because the big part of our game is working well at the moment.
"This is a different situation - definitely more enjoyable, yes - but I think that as a manager you need both to get better."
This weekend get a £10 free bet with Betfair, when you bet £10 on a Same Game Multi on the Premier League. Terms: Min £10 Same Game Multi bet on any EPL match this Fri - Sun. Free bet valid for 72 hours, awarded at bet settlement. Excludes cashed out bets. T&Cs apply.