Wheelchair-bound and barely able to talk in his later years, the South Africa legend passed away
Monday aged 45.
Motor neurone disease had left him a shadow of the gladiator who helped the Springboks win the World Cup in 1995, but his contribution to the game will never be forgotten, says former teammate Cobus Visagie.
"Joost basically created the new requirements for a modern No. 9," the former South Africa front-row prop told CNN's World Sport show Tuesday.
Van der Westhuizen was 6 foot 2 inches tall, but played at scrumhalf -- a position traditionally occupied by the game's smallest players, providing the link between teams' backs and forwards.
"Some days I looked down when we were standing in a circle and saw a man with boots three sizes bigger than myself -- a scrumhalf!" added Visagie, who played alongside van der Westhuizen at the 1999 World Cup and won 29 caps for his country.
"He had incredible speed, he had incredible bravery -- he's very well known for the tackles he made in the crucial 1995 World Cup, but also in all other games."
In the 1995 World Cup final against New Zealand, van der Westhuizen stopped a rampaging Jonah Lomu when the giant winger had broken through the South African defense.
The Springboks went on to win 15-12 in extra time, in the first major sporting event to be staged in South Africa after the end of Apartheid rule. The '95 side has achieved iconic status, notably through the Hollywood film "Invictus."
"Who could forget that '95 World Cup tackle?" former Springboks forward Alistair Hargreaves told CNN.
"He was fearless, and for a scrumhalf he certainly broke the mold. As a young boy, he epitomized what South African rugby was all about. We idolized him."
Courage on the field -- and off it
Van der Westhuizen was diagnosed with motor neurone disease in 2011, having retired from international rugby in 2003 with what was then a record 89 caps for the Springboks.
Also known as ALS or Lou Gehrig's disease, the condition causes muscles to weaken and waste away over time. In 2014 the "Ice Bucket Challenge" became a worldwide phenomenon, with millions of people helping to raise awareness and funds to research the disease.
Although he never played alongside van der Westhuizen, Hargreaves -- who left South Africa in 2012 to play domestic rugby in England -- was fortunate enough to have met his childhood hero later in life.
"I met him after his career and I probably met him at a time that his illness really kicked in," Hargreaves said. "If he was resilient on the field, he certainly proved to be resilient and even more courageous when he found out about the terrible circumstances he found himself in.
"What a brilliant battle he fought. You can only respect the man for what he did."
After his diagnosis, van der Westhuizen set up the J9 Foundation
, a charity dedicated to helping sufferers of motor neurone disease.
"It is incredibly sad, but Joost fought a long battle," Hargreaves added. "He was aware of the struggle he faced and I presume there is a certain amount of relief at the end of it.
"The guy has achieved so much, he's done so much for rugby, I'm sure they're going to hold him up as a real legend of the game."
A public memorial service will be held on Friday at Loftus Versveld Stadium in Pretoria, South Africa, the home ground of van der Westhuizen's provincial side the Blue Bulls.