Coolmore colt Switzerland has been all but ruled out of the rich Inglis Millennium.
The champion trainer says there is a "ninety per chance" Switzerland will not contest next Saturday's sales-restricted feature for which he is a $3.50 equal favourite in pre-nomination markets.
"It's a hard one, but I've just put the money aside and said, 'what do I do for the horse?' and that's what we're doing," Waller said.
"If he's to get to a Golden Slipper, he is going to have to do it in one prep, and I just feel two weeks after his first-up run isn't really fair on the horse.
"But if I go three weeks into his second-up run then three weeks into his third-up run and then we can go two weeks into the Slipper."
An impressive winner on debut last month, Switzerland is likely to have his next start in the Pierro Plate (1100m) at Randwick on February 17 with the Todman Stakes (1200m) at Randwick on March 9 slated to be his final lead-up to the Golden Slipper (1200m) at Rosehill on March 23.
Like Shinzo, who delivered Waller his maiden win in the world's richest two-year-old event last year, Switzerland is a son of Snitzel and is raced by Coolmore.
However, Waller said Switzerland was more precocious than Shinzo at the same stage.
"This horse is pretty sharp and pretty responsive, whereas Shinzo was all class and just got there in time," he said.
While Switzerland is unlikely to be seen this week, Shinzo is scheduled to step out in his first barrier trial of the preparation.
He has been entered for a 900m heat at Rosehill on Monday, although Waller says he might wait for the Randwick session three days later.
"He's in the trials on Monday but he has done pretty well and he might need one more gallop," Waller said.
Shinzo will resume in either the Group 1 Canterbury Stakes (1300m) on March 9 or the Newmarket Handicap (1200m) at Flemington on the same day.