Impressive acceleration almost proved River Delta's downfall in Saturday's Geoff Murphy Handicap at Caulfield.

River Delta went into the race unbeaten after easy wins at Yarra Valley and Flemington with another soft victory looking a formality in her latest assignment.

The three-year-old was well clear at the 300m but River Delta,the $1.95 favourite, lost focus and that allowed the runner-up Griante to cut her margin to a half-head by the finish.

Griante ($6.50) did not help her cause by drifting out under pressure in the final 100m.

River Delta pleased trainer Peter Moody with her win but the trainer said he would experiment with the filly's gear to ensure she kept her mind on the job in future races.

"She's in the unfortunate situation that not many horses can go with her," Moody said.

"She's never been pressured to the line and she gets lost."

Moody said he could look at backing up River Delta at Randwick next Saturday.

River Delta's narrow victory was crucial to apprentice Shaun Guymer, who moved from Sydney earlier this month to join Moody on a three-month loan.

It was Guymer's first win of his Melbourne stint.

Guymer said riding winners would help achieve his goal of staying in Melbourne once his loan period ended.