It's not something you often hear a horse racing trainer say but Dubbo's Peter Nestor knows how lucky he is to even have Not A Shadow on the track.

The four-year-old will jump from barrier nine in Saturday's $400,000 Country Championship Final at Randwick following a second-placed finish at the Western Districts Country Championship Qualifier at Dubbo on March 20.

But there's much more to Not A Shadow's story to that.

As a younger horse he was struck down by a severe virus, one which is still a mystery to Nestor, and it nearly claimed the life of the progeny of Not A Single Doubt and Helgafell.

The trainer admitted he "spent a fortune" trying to figure out what was wrong and tests were sent as far as Melbourne to try and solve it.

But eventually Not A Shadow's health improved and he is now in the running to earn a slice of Saturday's rich prize.

"I actually thought he could have been anything but he got pretty crook and nearly died and he's never really been the same," Nestor said.

"He's always been a bit up and down since then and I don't think he'll hit any great heights now and I'm under no illusions on Saturday but you never know what could happen, racing is a funny game.

"He most probably shouldn't be racing but he's done a good job and I think he'll be out of depth there but it will be a good guide as to how he's going."

Saturday will mark consecutive appearances for Nestor at Randwick.

Last year he made the trip with Dane De Lago for the inaugural Final but that day didn't go exactly to script.

An exhausted Dane De Lago finished 13th after a rain-affected preparation but things are more positive for Nestor this time around.

"At least he's on the way up," Nestor said of Not A Shadow.

"Whereas the other horse (Dane De Lago) was at the end of his tether and he really finished after the Dubbo heat and even in his last prep that showed, he still looked a bit tired."

Nestor will be reunited with jockey Kathy O'Hara on Saturday with his former apprentice agreeing to take the ride.

Not A Shadow will carry 56kgs, the same he did in the Dubbo qualifier.

"Kath doesn't too much wrong and does what she's asked, that's a big thing," Nestor said.

"She's consistent."

The Country Championship Final is the fifth race on the card during day one of The Championships at Randwick and jumps at 1.55pm.