Speediness is coming into the best form of his career as he enters the Group One Sir Rupert Clarke Stakes on Sunday, says trainer Colin Scott.

Scott admits it's a big step up in class for the six-year-old gelding he bought as a yearling but says there is enough form around the son of Testa Rossa to suggest an upset could be on the cards.

"The form around him has been sensational but this horse owes us nothing," Scott said.

In his last four starts Speediness has won two Listed races and a Group Three - the Bobbie Lewis at his last start on September 7 at Flemington, beating Sir Rupert Clarke entries Temple of Boom and Rebel Dane for good measure.

In May, Speediness ran third to Mouro and Beaten up in the Rowley Mile at Hawkesbury.

Beaten Up went on to win the Doomben Cup and then Speediness turned the tables on Mouro in winning the Scone Cup.

"We've been very patient with him and he is probably now just starting to show his true potential," Scott said.

One problem for Speediness is his barrier 14, but a philosophical Scott said it could have been worse because there are another four horses outside him in the capacity field of 18.

"If you draw wide at Caulfield over 1400 metres it is never ideal," Scott said.

He said he will leave the tactics up to experienced jockey Craig Williams, who rode Speediness to victory in his first race in Sale back in August 2010.

"My job is to have the horse turn up in the best condition it can be and for Craig to do the rest," Scott said.

Speediness has been nominated for the Group One Cox Plate next month but Scott admits the Group Two Crystal Mile over 1600 metres, run on the same day, looks ideal for his horse.

"We certainly wouldn't shy away from the Cox Plate, but it is a big step up in grade," Scott said.

Rebel Dane is early favourite at $5 while Speediness is a $11 chance.