The Austrian was tasked with guiding Southampton to Premier League safety when he replaced Mark Hughes in December.
Hasenhuttl achieved that objective as Saints finished five points clear of the bottom three, winning eight games under his tutelage, and he is hoping to build further momentum next season.
The early signs look good for Southampton after the squad started to get to grips with his high-pressing approach, but the former RB Leipzig boss knows more quality is required.
Hasenhuttl told the club's official website: "It's big because there is a lot of work to do. We know this, and it is important that we change the team a little bit and bring new players in.
"Having a few new inputs, also for our mind, is what we will do this summer."