The Croatian footballer was celebrated as a miracle testament to determination and the skills of doctors after returning to professional soccer following the transplant last March.
But German weekly news magazine Der Spiegel reports today that he has launched legal action against Götz Dimanski and Manju Guha.
He says they not only failed to realize that his kidneys were losing function, but also continued to give him the painkiller Voltaren, which is very bad for kidneys.
Had they seen what was going on with his kidneys, he could have delayed the need for a transplant – and the heavy, ongoing drug regime that requires - by several years.
They deny any responsibility, saying the progression of his condition was due to genetics.
Klasnic was the first professional footballer to play after a kidney transplant.
He had two transplants, after the first kidney donated from his mother was rejected by his body and he received a second from his father.
But despite being in the care of doctors at Werder Bremen, the extent of Klasnic's kidney trouble was only spotted when he was admitted to hospital with appendicitis and doctors treating him looked as his blood.
“His appendix, that was our stroke of luck,” his wife Patricia told Der Spiegel later. “If Ivan had not gone to hospital because of that pain, he would have probably have dropped dead on the pitch one day.”