But Rotorua Half Ironman director Shane Hooks persuaded Mr Slade to give his event a go. He finished the event in 6h and 4s, which gave Mr Slade the confidence to try the full Ironman event - his eighth - this Saturday.
It may sound like a dream recovery, but Mr Slade, who now has a plate holding his hip together, says he has both physical and mental reminders of the attack. After 160km or so on the bike on rough chip seal, his hip aches from the constant vibration.
He hasn't trained as much for this Ironman as he has done in past years because he has to allow plenty of recovery time. He's still nervous when he's out training on the bike.
Because of the attack, Mr Slade also gave up his job as a Corrections officer at Tongariro-Rangipo Prison.
He's now a caretaker at a local school, a job he loves. He says he felt he could no longer fulfil his prison role properly.
"I didn't feel 100 per cent physically and mentally able to respond to emergencies the way the job demands ..."
If this Ironman event goes well, there will only be two more to notch up 10 Ironman events, and Mr Slade says although it's an alluring thought, he has to see how this one shapes up first.
He hasn't seen the orthopaedic surgeon who repaired him, Steve McChesney, for many months now but says while Mr McChesney is a fine surgeon, he's also a great psychologist. After the hip operation, Mr McChesney told Mr Slade his running days were over. It was like a red rag to a bull. "I think I might send him a thank you card after this is done."