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On paper it may look as if the All Stars trotter is set to complete just another perfectly-plotted path to big race glory for trainers Mark Purdon and Natalie Rasmussen.
However, a look further back shows the exciting trotter has had to overcome odds exponentially higher than what he will pay to win the 3200m feature, just to be in the race.
Oscar Bonavena needed a miracle just to be a racehorse, and Purvis was the driving force behind making it happen.
The Majestic Son trotter was born weak and unable to stand on what vets deemed were legs too crooked for a potential racehorse.
Vets' advice to Purvis's father, John, who bred the horse, was that the foal's chances of being a successful racehorse were slim because of his crooked legs and his missing out on vital colostrum-enriched milk from his dam immediately after being born.
Purvis told her father she was not having any of that talk, and continued to hand-feed the foal.
"... I told Dad he wouldn't be worrying about any of that and I kept looking after him," she said.
After helping keep the foal alive, Purvis handed over duties to Nevele R Stud staff, who continued to help Oscar Bonavena get on his feet.
"After a couple of days we were able to get the mare and foal to Nevele R and they kept feeding him.
"Eventually he was strong enough to stand on his own and then drink off his mother.
"As he got older his legs got stronger and he was perfectly healthy."
Purvis' early work with the trotter meant he was almost certain to end up in her care.
Her father sent her the trotter, and Oscar Bonavena was to be a "project horse" for the horsewoman and her partner, reinsman Matthew Williamson.
Oscar Bonavena soon showed the only project he was concerned about was running fast.
He went on to win his first start as a 2yr-old, before being sold by John Purvis in a big money deal that transferred him from Phil Williamson's barn to the All Stars stable.
Months later his new owners faced similar vets' advice about Oscar Bonavena to what the Purvis family had received earlier - that his legs were not up for racing.
Some high-level veterinary research, coupled with Purdon's genius horsemanship, combined to help Oscar Bonavena recover from the potentially career-ending injury.
The troubled knee has held up so well since that it has allowed him to catapult to the top of the New Zealand trotting ranks in his seven starts since May.
And apart from one standing start mishap - that did not stop him winning - everything has gone perfectly.
"He had a great preparation and I think when we nominated him he was about 45th in the ranking for the Dominion and now he is right up the ladder and come in to favorite," Purdon said.
"So he has had a great prep and I couldn't be happier with him."
Purvis and her father will also be on hand to watch Oscar Bonavena's first attempt at open class group 1 racing. The thrill they will get if he is able to win will be just as big as if the trotter was still officially theirs.
"We will be there and it will be very exciting - I still get a huge thrill from seeing him race," Purvis said.
"Every time I am at the races and he is in I go down and see him, I can't wait."