The element of surprise will be missing when Empress O'Reilly resumes at Saturday's Moonee Valley meeting.

Empress O'Reilly stunned punters with a $26 debut win at Caulfield on Boxing Day in a performance that also surprised trainer Robert Smerdon.

"We thought before that first-up run that she'd need it and take good improvement but she ended up winning the race," Smerdon said.

Smerdon sent Empress O'Reilly to the spelling paddock to develop further before bringing the filly back to start her three-year-old season in the National Jockeys' Celebration Day Handicap (1000m).

Bookies have welcomed the opportunity to assess Empress O'Reilly's form and have her as the $4.40 favourite to remain unbeaten.

As her name suggests, Empress O'Reilly is a daughter of New Zealand-based stallion O'Reilly, the sire of Caulfield Cup winner Master O'Reilly, top staying mare Silent Achiever and ATC Australian Derby winner Shamrocker.

Smerdon noted O'Reilly's progeny are effective over ground but said Empress O'Reilly has bucked her breeding slightly with her solid physique.

"She is a sprinting type," Smerdon said.

"She's a really neat solid type so it depends how far she can take her speed I suppose."

Debut winner Lexgetreddy will join Empress O'Reilly in the race, the filly's first outing since a dismal trip to Adelaide in April.

Lexgetreddy won easily at Sandown in March but her manners deserted her at her first attempt to gain an important Listed win when she finished seventh in the Dequettville Stakes at Morphettville.

"She's done well since she came back into the stable," Smerdon said.

Smerdon has engaged apprentice Jackie Beriman to take 2kg of Empress O'Reilly's 60kg impost while Mark Zahra will partner Lexgetreddy.