The consensus verdict a fortnight ago was that the Blue Diamond Preludes had left us with more questions than answers.

That statement can usually be translated as, “We got our tips wrong.” Regardless, we head into this Saturday’s Blue Diamond with an open market. Big Sky, who didn’t race on Prelude day, is the favourite but at near enough to each-way odds.

This lack of certainty on Diamond day is a trend, but only a recent one.

Melbourne’s premier two-year-old race was an open book to punters from 2011 to 2018, with six winning favourites in eight years.

The recipe was simple. The Diamond winner would be having its third or fourth start and 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 seven years has been $14.36.

Defying my formula were Tagaloa (fourth in the Prelude), Daumier (third in the Prelude), Artorius (last-start Sandown midweek winner), Hayasugi (won the Prelude, but was having her fifth start in the Diamond) and Devil Night (second in the Prelude, but the Diamond was only his second start).

The main lead-ups rank in the following order when it comes to the winner’s strike rate in the main event: fillies’ Prelude (10/38, 26%), males’ Preview (8/32, 25%), Chairman’s Stakes (3/16, 19%), fillies’ Preview (4/29, 14%), males’ Prelude (5/37, 14%).

This year’s respective winners are Streisand, Alibaba, Big Sky, Rubi’s Choice (not running) and Closer To Free.