Blue Diamond Stakes winner Catchy has opened favourite for the Thousand Guineas but may run in the more lucrative Caulfield Guineas on the same day.

Lindsay Park is still yet to decide whether come October 14 the filly, who is unbeaten in Melbourne, will take on the boys or stick to the fillies-only mile.

The TAB has her at $9 for the $500,000 Thousand Guineas ahead of stablemate Tulip and Percy Sykes Stakes winner Shoals at $13.

The TAB signalled how highly it rates the chances of Godolphin's Alizee, also placing it $13 - half the price of that offered by one corporate bookie.

Catchy features prominently in the market for the $2 million Caulfield Guineas, where she is alone on the third line of betting at $13 behind clear favourite Royal Symphony ($7).

Four runners - Blue Diamond runner-up Pariah, ATC Sires' Stakes winner Invader and lightly raced Godolphin duo Esperance and Kementari - are all at $11 for the three-year-olds' mile.

Catchy is also in the market at $26 for the $10 million Everest (1200m) at Randwick on the same day.