"Following the match against the Pumas on Saturday, Bakkies went for a scan where it was confirmed that he ruptured his posterior cruciate ligament," said Andy Marinos, South Africa's manager of national teams.
"He was seen by an orthopedic specialist who advised that we adopt a conservative management of this injury and as such the player will not undergo an operation but will commence immediately with rehabilitation.
"He has, however, been ruled out for the rest of the Tri-Nations competition and the majority of the Currie Cup. We are hopeful that he will be fit again for selection for the end of the year tour to Europe."
Last Saturday's clash with the Pumas in Johannesburg was Fourie's first appearance in Springbok colours this year but the 25-year-old now faces another frustrating lay off after an accidental clash with José María Núñez Piossek at Coca Cola Park.
"Following a clash of heads between Jacque and the Argentinean left wing, a ST scan revealed a fracture to the right cheekbone," said Marinos.
"This is a depressed fracture which will require surgery this week. Following his operation, Jaque will then be out of action for six weeks."
As a result of the injuries to Botha and Fourie, South African head coach Peter de Villiers has called up Danie Rossouw and Francois Steyn for next Saturday's Tri Nations match against New Zealand and the double-header with Australia.
However, both Rossouw and Steyn are themselves struggling with minor injuries and will not take place in Springbok training this afternoon.
After playing for the Blue Bulls against the Golden Lions, Rossouw spent Friday night in hospital where was examined and cleared by a specialist. He is expected to be back in full training on Tuesday, while Steyn will also be missing from the initial sessions after picking up a hematoma in his quad during the Sharks' win over Western Province.