In the most open Jockey Challenge market ever framed, top rider Brett Prebble makes great appeal at an opening quote of $7.50.

The eight favoured riders' opening odds range between $7 and $9, and with little separating their rides on form, punters should play the man and stick with the king of the Valley.

Prebble has five chances - Many Gains, East Ocean, Vilasol, Flying In and London China Town.