Caulfield Guineas winner The Autumn Sun will not tackle stablemate Winx in the Cox Plate with connections citing his immaturity as a factor.

While John Messara, whose Arrowfield Stud owns 50 per cent of the colt, says he doesn't want to be the one to shoot Bambi if The Autumn Sun should beat Winx, trainer Chris Waller believes it is in the best interests of the three-year-old to be given a break now.

"The fact is, it's a pretty tough ask," Waller told NZ Trackside radio.

"I just don't think he needs that pressure just yet and we are best waiting for a little bit longer.

"He's not, to my eye, he's not fully developed yet. He's going to round out and thicken up.

"Winx is rated the world's best so he has to be the world's best to beat the world's best.

"Why put a horse through the pressure when they're not ready for it."

The Autumn Sun, who weighs 480kg, was foaled at Arrowfield and is a product of the stud's enduring champion Redoute's Choice.