Andreasen preparing for 'tense' Hamburg clash
The Bundesliga side currently sit in 11th place after the opening 12 league matches of the season, with a good start marred by a recent six-match winless streak.
Hannover have also struggled defensively of late, conceding eight goals in their previous four outings, as well as having lost all five of their away games in the Bundesliga this term.
Midfielder Andreasen knows Hannover will have to be at their best this weekend to pick up points on their travels for the first time since April.
"We are under pressure, we have to play well on Sunday. The atmosphere is tense, you feel that," he told Sky Sports News.
Hannover's poor run of form has also seen the pressure mount on manager Mirko Slomka, but Andreasen feels that the players need to take responsibility too.
"Of course he is also under pressure. But we have good players on every position, so it’s not about him," he added.