It took trainer Neil Walsh a while to work out that his talented galloper Zuma Roc wasn't the horse he was supposed to be.

Armed with the vital discovery and a horse who is at the peak of his form, Walsh is more than hopeful Zuma Roc can repeat his Flemington win of two weeks ago when he steps out in the Gala Supreme Handicap (2000m) at the track on Saturday.

"He's out of a very good mare who was a real mudlark," Walsh said.

"But it took us a while to work out that he didn't handle it."

With his wet-track theory in mind and a win over the Moonee Valley 2040m to boost his hopes, Walsh set the horse for the Tasmanian Derby.

But along with a failure on a slow track in his lead up came the realisation that Zuma Roc hadn't inherited his mother's liking for mud.

It is a situation that threatens to present the trainer with a dilemma on Saturday thanks to weather reports that range from showers to thunderstorms and hail.

"If it comes up a dead four then he'll run," Walsh said.

"But if its any worse, I'll pull him out."

Should he run, Walsh is confident Zuma Roc can repeat the last-start win that was the best of his career.

"It was a really good, strong win last start," he said.

"The thing about him now is that he's a lot more versatile and that gives us the option of going forward if we need to or staying back off the pace if its too hot."

The Flemington track was rated dead late on Friday.