New Zealand apprentice Sam Weatherley has made an immediate impression in Sydney, riding She Knows to win at Randwick.

The 19-year-old has begun a three-month stint with Chris Waller at Rosehill and the Danny Williams-trained She Knows was the last of his three rides on Saturday.

The filly started at $3.40 in the 1000m-sprint with Weatherley's two kilogram claim getting her in the race with 56.5kg.

Weatherley had time to savour the moment, with She Knows well clear as she strode to a 2-1/4 length win over Noble Joey ($19).

"It's a huge thrill to make a mark so early," Weatherley said.

"And to ride at Royal Randwick is amazing.

"We watch the races at home and Randwick is the pinnacle.

"This is a huge confidence boost and it means a lot.

"Danny Williams told me to back myself and just ride her how she felt."

The heavy track was also no problem for Weatherly.

"The tracks are so different here and this would be slow at home."