The former Blue Bulls and South African team mates were involved in separate incidents. Scrum half van der Westhuizen was admitted to Sunninghill Hospital after collapsing at his Johannesburg home shortly after returning from Loftus Versfeld.
The 38-year-old was complaining of chest pains and was reported to be in a stable condition after arriving at the hospital.
Kruger, meanwhile, fell unconscious at the wheel of his car as he was driving home his wife and two children. The 39-year-old former back row star recently had a brain tumor removed.
He was admitted to the intensive care unit at Pretoria East Hospital, where he was in a serious but stable condition. He suffered serious head and facial injuries in the crash, although his wife and two daughters received only minor injuries.