Some 11 months later Jacob has secured selection for the Rio Paralympics.
"It is still pretty surreal," admits Jacob, who last week was selected on the New Zealand team to compete at the 2016 Paralympics. "I'm proud of everything."
Born and raised in Hamilton, Jacob grew up in a sporty family and he never let his slight co-ordination and balance issues associated with cerebral palsy discourage him from trying his hand at a number of sports.
From the age of seven he played soccer and after participating in a number of 'Have a Go' events organised by Paralympics NZ he discovered an interest and talent for athletics.
In 2011 aged "14 or 15" he decided to pursue the sport more seriously and hooked up with Hamilton-based coach Alan McDonald. He started out as a middle-distance runner and also competed discus, shot and javelin. He earned some success banking an 800m silver medal at the 2013 Queensland State Championships and a bronze in the shot at the 2014 Australian Championships.
Yet later that year he experienced what he describes as a "turning point" in his career when a change in his classification from a T38 to a T35 athlete gave him limited options as a middle-distance runner and he switched to the sprints.
"Luckily I had done some sprint work as a middle-distance runner," he explains. "It took a while to adapt to the shorter, faster stuff, but the change wasn't too bad."
He showed promising signs in 2014 and targeted a spot at the 2015 IPC Athletics World Championships in Doha and early that year moved down to Dunedin to start a PE degree at the University of Otago. Only to then be struck by the devastating shock of the cancer diagnosis.
Yet he always retained a positive outlook. He gave time and energy to his running future and maintained his fitness as best he could.
"I couldn't sprint for 100m, but I did small doses of activities where I could such as walk to the shops or a bike ride," he explains. "Athletics was still a big part of my life and in 2015 I was still following the other (para) athletes. They gave me inspiration and hope I might one day achieve as well."
Following the all-clear in August 2015 he returned to training. Now coached by Dunedin-based Brent Ward - coach to Paralympic-bound long jumper/sprinter Anna Grimaldi - but still advised by McDonald, a man whom Jacob calls "an inspiration," he tentatively returned to training last August.
It took time to adapt to the demands of training. During the treatment process he had shed 4kg in body mass and had consequently lost strength. Yet as his appetite returned he started to pile on the weight a
"When I re-started training the Rio Paralympics were still a year away, but to be honest I expected a (domestic) season of re-building and I was looking towards Tokyo (Paralympics in 2020)."
Following his recovery from cancer his training was stripped back to basics. Much of the technical work was re-learned. Only later was greater volume introduced.
"The technical work was one of the fundamental things which helped me recover (my form) quickly and came back with even faster speed," explains Jacob. "We worked on many aspects of technical work - even simple arms and high knees."
Training "five or six times a week" with a combination of track work, grass and hill sprints and gym work, Jacob showed he was back better than ever competing in his hometown of Hamilton at the Porritt Classic in February.
There Jacob dismantled his 200m best by 0.37 to run 29.10 and he also chipped 0.12 from his 100m best to record 14.11. Later at April's Australian Championships, Jacob dipped under the A qualifying standard for the 200m with a 28.98 PB performance and a B standard 100m with a 14.05 clocking.
Due to the convoluted qualification process and ranked just outside of the world's top ten in the 200m - his stronger event - the teenager never expected a nomination for the Rio Paralympics.
So when he found out he had secured selection last week for the Rio Paralympics, it came as a huge shock to the former Hamilton Boys' High School student.
"It is going to be an amazing opportunity," explains Jacob, who also harbours a long-term ambition to work in a role to encourage more youngsters with a disability compete in sport. "In some ways these Games will be about gaining experience but obviously I hope to compete as well as I can before looking to future Games, where I hope to be in medal contention."