Bischoff is now facing a race against time to be ready for pre-season training at the beginning of July.
"I went into a tackle with the interior instead of the ankle," said Bischoff.
"According to the doctors, the ligament came apart from the bone. I am very sad about the timing because I had looked forward a lot to the two internationals coming up.
"On the other hand, the timing is not all wrong since it is vacation after the internationals and I am glad that the doctors judge that I will be back in six to eight weeks."