The Saints made a flying start to the campaign and even led the Premier League table in the autumn but have struggled since the turn of the year, something that Hasenhuttl blames on a threadbare squad.
The Southampton boss told Sky Sports: "Because of the depth we have, we haven't been able to rest players out of form, so we have had to continue.
"After that, it's normal that we have some problems in having consistently high performances.
"When you're struggling a bit with performances, you automatically lose a bit of self-confidence, and with the ball especially. We have some players who have been full of belief and everything was working well, but after injuries and a few games we haven't won, it's not been the same.
"It's not surprising that it's happened, we see it all around, in other teams too - I've seen the champions doing that this season, and we are Southampton."
Hasenhuttl has now challenged his team to replicate their strong finish to the end of last season by picking up as many points as possible in the closing weeks of the campaign.
He said: "The first half of this season was also very successful. We played football in a way we haven't shown since I was here, very dominant, really creating some respect for our game. You could feel it when teams were playing against us, but with injuries over Christmas, with seven, eight, nine players out with injury, everything dropped massively.
"Last season we won a lot of points in the final seven or eight games, and that's the goal for this year too."