Another wide-open Blue Diamond is heading our way this Saturday, with the market unable to make up its mind which form line is strongest.

This is only a recent trend. Melbourne’s premier two-year-old race was an open book to punters for a while there, with six winning favourites in eight years from 2011 to 2018.

The recipe was simple. The Diamond would be won by a horse having its third or fourth start, coming off a quinella finish in a Blue Diamond Preview, a Blue Diamond Prelude or the Melbourne two-year-old race three weeks before the Diamond (once the Talindert, now the Chairman’s Stakes).

That formula produced 12 straight winners including Reaan (2008), Reward For Effort (2009) and Star Witness (2010) at double figures.

Recent winners have been more of a mixed bag. No favourite has won since Written By ($5.50) in 2018, and the winner’s average SP across those six years has been $14.08.

Defying my trusty formula were Tagaloa (fourth in the Prelude), Daumier (third in the Prelude) and Artorius (last-start Sandown midweek winner).

Last year Hayasugi became the first since Sepoy (2011) to complete the Preview-Prelude-Blue Diamond treble, but she didn’t quite fit the formula as the Diamond was her fifth start.

Somehow Hayasugi was allowed to go around at $16, presumably because the conventional wisdom was that the colts were better. Coleman started the $3.40 favourite and ran 13th.

In closing I’ll note that the main lead-ups rank in the following order when it comes to the winner’s strike rate in the main event: fillies’ Prelude (10/37, 27%), males’ Preview (8/32, 25%), Chairman’s Stakes (3/16, 19%), fillies’ Preview (4/28, 14%), males’ Prelude (5/36, 14%).

This year’s respective winners of those races are Palm Angel, Shining Smile (not running), Inkaruna (not running), My Gladiola and Field Of Play.