A start in Melbourne's richest race for two-year-olds is on the line in the respective divisions of the Blue Diamond Preludes at Caulfield.

The youngsters run in separate heats on Saturday, one for fillies and the other for colts and geldings, to try to make the final field for the $1.5 million Blue Diamond Stakes at Caulfield on February 27.

Cohesion guaranteed himself a start in the Blue Diamond when successful in the Preview for colts and geldings at Caulfield on January 26, and he again lines up on Saturday.

The fillies Preview winner, Sword Of Light, is not among nominations for the Blue Diamond and has drawn the outside gate on Saturday.

If she can win the Prelude, connections are likely to pay a $55,000 late entry fee to contest the big race.

Impressive Moonee Valley debut winner Zamzam is No.24 on the order of entry for the Blue Diamond and victory in the Prelude will guarantee her a start.

Extreme Choice is the $2.70 Blue Diamond favourite after his impressive win at Caulfield in the Chairman's Stakes last Saturday.