Darren Weir is hoping a much-improved Big Duke can clear another significant obstacle at Randwick and break more new ground for the leading Victorian trainer.

The five-year-old gave Weir a maiden victory in Sydney in the Manion Cup at Rosehill on March 18 before claiming the $300,000 Chairman's Handicap (2600m) last Saturday.

Big Duke is now striving to extend his current winning streak to four - a sequence that started in February's Launceston Cup - in Saturday's Sydney Cup to give Weir his first elite level win north of the border.

Encouragingly for Weir, Big Duke has done enough over this preparation to warrant favouritism despite never being tested over the 3200 metres.

Weir, who took over training the former English horse last November, credited separate trips to Tasmania for the Hobart and Launceston Cups for developing the horse into a progressive stayer.

"He had his chance in the Hobart Cup (and finished second). Obviously the winner (Count da Vinci) was too good on that day but the horse has made really good progress since then," Weir said.

"I guess the trip away made him grow up because he had the two trips over and back and then over and back.

"When he went over the second time he was much better in himself and he raced that way. He's gone on since then."

Weir said Big Duke had exceeded expectations ahead of a well-earned spell.

"I guess he might have taken bigger steps than we sort of thought in this preparation. Everything we've put him in, he's run well," he said.

"It's just nice to have him in a good race and the end of a good prep."

Weir said the handicappers had also worked in his favour with Big Duke, to be ridden for a third time by Craig Williams, only carrying 52kg on a track that could improve from heavy to soft.