They instead dragged him to the side of the road into nearby bushes.
After the attackers vanished the sportsman was able to crawl onto a main road where a security driver spotted him.
Jackson told The Guardian that Gwala had overcome drug and alcohol addictions to represent South Africa at worldwide competitions in Chicago in 2015 and in the Netherlands previous year.
The motive for the attack is not immediately known.
The assailants began cutting into Gwala's left leg before they fled, allowing the athlete to crawl to a road and flag a passing auto. "When they saw it was getting stuck they started on the other leg", Shange continued.
While others suggested the attack could have been carried out in the name of "muti", a term for traditional medicine found in South Africa.
"One was armed with a firearm and they attempted to cut off his legs with a chainsaw".
"We don't yet know how far they went in‚ whether they were trying to cut it off‚ or what the circumstances are".
The athlete's training partner Sandile Shange has told the BBC that Gwala had been involved in a potentially-fatal attack involving a chainsaw and an attempt at amputating his prized set of limbs. "The surgeons are confident", Dennis Jackson, head of South Africa's Elite Athlete Development Programme, told AFP. Jackson said. "From what we understand‚ he is in a cast". Absolutely disgusting! How safe are we on SA roads?
A crowdfunding campaign has been started with the aim of raising funds for the Durban triathlete who nearly had both his legs cut off with a chainsaw on Tuesday.
The BBC News wrote that Gwala expected to participate in the South African national championships this month.
Gwala is a strong contender for the race which is a 40k cycle, 10k run and 1.7k swim.