Cessnock trainer John Bannister has reconditioned the retirement-bound Jackknife into an unlikely Highway Plate contender.

Bannister, who has five horses in work, a team he happily describes as "reject, giveaway" horses, heads to Rosehill with his second city runner on Saturday as Jackknife attempts to add to his recent win at Moree.

Jackknife was set for a switch to eventing before Bannister convinced his owner to keep racing through a leasing arrangement.

The trainer had seen enough in Jackknife's runs to believe he could rejuvenate the four-year-old, and the horse responded by following three encouraging placings with his victory over 1300 metres at Moree on July 20.

"He just needed a change of environment. When I first got him (in January) he was a lunatic," Bannister said.

"You couldn't do anything with him, now he's a completely different horse.

"He just had to change his mind-set around."

Bannister also used acupuncture to address muscle soreness.

Jackknife was rated as a $13 chance with the TAB on Friday ahead of the step up to 1500m.

Second placings behind Buddy Honest and Cosmic Reign at Quirindi and Muswellbrook convinced Bannister a trip to Sydney was warranted after that duo subsequently finished first and fourth respectively in a Highway Handicap at Rosehill a fortnight ago.

"It's a harder race for him but he was sacked as a racehorse so win, lose or draw I'll still be happy with him," he said.

Jackknife is Bannister's second bid at a Highway after Miss Tickles finished 10th at Rosehill last year.

The six-year-old was still a success story for Bannister who paid $900 for her in May, 2015. In 43 starts she has amassed $96,352 prize money.