Sunderland have suffered defeats in three of their four pre-season games, and Larsson has demanded that the team must improve quickly.
After the defeat to Helsingborgs at the weekend, Larsson said: "It was a very poor performance. We were well below-par.
"We know that we need to get at least another 20 to 30 levels up before we are ready to compete in the Premier League."
Sunderland complete their pre-season schedule with matches against Derby County and Leicester City.