The Thousand Guineas Prelude will determine the spring path for Moonee Valley winner Merriest.

The Danny O'Brien-trained three-year-old took out the Listed Atlantic Jewel Stakes on Saturday, her second victory from four visits to the racetrack.

Ridden by Damien Oliver, Merriest ($26) sat outside the leader before scoring a short-head win from the $5.50 Whispering Brook with Sweet Sherry ($9) 1-1/4 lengths away third.

The victory gave Oliver the second leg of a winning double having scored on Vostok in the United Refrigeration Handicap.

Merriest will contest the Thousand Guineas Prelude (1400m) at Caulfield on September 24 which will then decide if the filly presses on to the Thousand Guineas (1600m) on October 8 or stays to shorter trips.

"She settles on the pace and relaxes in the run so we'll try her at 1400 metres in the Thousand Guineas Prelude and then that will give us a good idea," O'Brien said.

The trainer expects the filly to make further improvement with Saturday's win under her belt.

Merriest finished eighth first-up in the Quezette Stakes at Caulfield on August 13 and was sent out the third roughest on Saturday.

But O'Brien said Merriest was luckless first-up.

"Damien today had her up on the pace and she showed plenty of fight," O'Brien said.

Oliver expects the 1400m of the Thousand Guineas Prelude to be no problem for the daughter of Denman but holds some concerns about her running 1600m.

"She might just be a bit brilliant for the mile," Oliver said.

Merriest had her price trimmed from $51 to $31 for the Thousand Guineas while runner-up Whispering Brook firmed from $21 to $15.

O'Brien returns to the Victorian Civil and Administrative Tribunal on Monday as his appeal against a four-year cobalt conviction resumes.