Former Springbok captain and scrum-half Joost van der Westhuizen died on Monday after his long battle with Motor Neuron Disease.
He was 45 years old.
On Saturday Van der Westhuizen's J9 Foundation confirmed that he was rushed to hospital in a critical condition.
Blue Bulls chief executive Barend van Graan confirmed Van der Westhuizen's passing and sent his condolences to his children, family and friends.
"If there's one thing we can learn from Joost it was his passion for life," Van Graan told Sport24.
"That we will never forget."
Van der Westhuizen, who was diagnosed with Motor Neuron Disease in 2011, is rated as one of the game's finest ever scrum-halves. He represented South Africa in 89 Tests and scored 38 tries.