Trainer Peter Snowden's chances of winning a third Golden Slipper have been diminished with Stratosphere now a non-starter during the Sydney autumn carnival.

Snowden, who trains with his son Paul, told Racing NSW stewards on Friday the two-year-old would be spelled to prepare for a spring campaign.

Stratosphere had been 40th equal on the order of entry for the $3.5 million Golden Slipper (1200m) at Rosehill on March 24, and rated a $15 chance on the TAB futures market.

The colt made a promising start to his racing career when edged out by a nose in the Group Three Canonbury Stakes (1100m) at Rosehill by Performer on February 3.

Performer is the $7 second elect for the world's richest race for two-year-olds behind the Magic Millions 2YO Classic winner Sunlight at $6.

The Snowdens still have Neutrality as a $26 chance for the Golden Slipper and $1.3 million yearling Tchaikovsky launches his bid to qualify in the Pierro Plate at Randwick on Saturday.

Peter Snowden won the Golden Slipper with Sepoy in 2011 and then celebrated Capitalist's win with his son in 2016.