NAC dealt Peto blow
The Hungarian picked up a knock against PSV Eindhoven a fortnight ago, but the club were initially confident he had suffered only minor damage.
However, extensive tests revealed serious damage to the cruciate ligament in his right knee which facilitated a complete reconstruction.
Peto suffered a similar injury at the start of last season and it would appear as if he aggravated an existing complaint.
"One of the two areas that were reconstructed before was torn and the other was bleeding," orthopaedic surgeon Alex Fievez told NAC's website.
"It was no longer stable and could not be trusted, so we decided to go for a total reconstruction.
"We have reconstructed the cruciate ligament with part of a tendon from Tamas' knee cap.
"It all looks good and we have found no other damage in the knee. Both the cartilage and the meniscuses appear fine.
"It is tough for Tamas at the moment, but I'm convinced he will make a complete recovery.
"There is nothing to worry about, but it will take time.
"The time-scale I have set is for a half-year period of recovery. Hopefully he will be able to return at the winter break."