Liverpool appeared to be Chelsea's main rival in the race for the Premier League title earlier this season, but one win in 2017 has seen them drop to fifth place in the table.
They were comprehensively beaten 3-1 by Leicester City on Monday and Hamann feels Liverpool are too one-dimensional under their German coach.
"At this moment in time, Liverpool under Klopp are one-dimensional, that is why they find it hard to win when things are not going their way," Hamann told Paddy Power.
"What has happened in the last seven or eight weeks - with only a single victory for the Reds in both January and February - has been pretty disastrous. Something has got to change, because if they carry on like this things will get a lot worse.
"The physicality and intensity is much higher in England than anywhere Klopp has been before. You cannot outrun teams in the Premier League, full stop. That is something the players and the manager have to learn, because they can only play one way.
"You need to be flexible, variable and overall you must have two or three answers to the questions teams in this league will ask of you."