Back-to-back wins have not yet given Chris Waller an accurate gauge on Scream Park's capabilities as he targets a $1 million race in New Zealand.

The New Zealand-bred three-year-old colt won his second successive race at Warwick Farm when claiming the Boxing Day at Royal Randwick Handicap (1600m) by 2-3/4 lengths but Sydney's premier trainer said it was still difficult to determine how he measured up.

"His maiden win was on a wet track and he drifted out wide, today he struck a three-horse field," Waller said.

"We do think he's got a lot of ability, it's just hard to measure against a small field and wet tracks."

Scream Park, the $1.40 favourite, still resisted the challenge of Colesberg ($5.50) and Choice Harvest ($4.60) in encouraging fashion.

"He had to sustain quite a long sprint, it was really good to see he had a high cruising speed, then he drew away it the last bit," Waller said.

He hoped for a larger field when Scream Park has his final tune-up for the Karaka Million 3YO Classic (1600m) in Auckland at Warwick Farm.

Waller picked out the January 6 meeting hours before today's race morning as a final audition for an assignment at Ellerslie three weeks later.

"We had a quick look this morning, which is always a good sign before a race, confidence from the trainer," he said.