A strong staying win in wet conditions at Rosehill has propelled import The Offer to the head of Sydney Cup betting.

The Gai Waterhouse-trained The Offer revelled in the heavy ground to add Saturday's Group Three Manion Cup (2400m) to his first stakes win in the Ballarat Cup last spring.

He is now the $4.60 favourite for next month's Group One Sydney Cup (3200m).

"He's a top stayer on the rise and something like the Sydney Cup definitely won't be out of his reach," jockey Tommy Berry said after partnering The Offer an emotional win.

Berry returned from Singapore where his twin brother Nathan is seriously ill in hospital to ride at Saturday's meeting.

Nathan Berry has been diagnosed with NORSE syndrome which causes severe seizures and placed in an induced coma.

Tommy said it was hoped Nathan's condition would become clearer in the coming days.

The Offer settled off the speed in the small field but after Berry asked him to improve into the race approaching the home turn, he picked up and had the race in his keeping early in the straight.

Waterhouse said The Offer was an exciting stayer in the making.

"He won the Ballarat Cup as a very green individual," Waterhouse said.

"He came from Aidan O'Brien's yard in Ireland and Rob (Waterhouse) picked him out on form.

"I knew he would love the ground, because I thought `if you were trained in Ireland you'd be used to a bog'."

A son of Montjeu, The Offer took his record to four wins from 15 starts and his record on heavy tracks to three wins and a second from four attempts.

Ranvet Stakes winner Silent Achiever is the $6 second favourite for the Sydney Cup with imported Irish mare Voleuse De Coeurs and Zipping Classic winner Sertorius at $8.

The Sydney Cup market is likely to get another shake-up after Saturday's Group One BMW (2400m) at Rosehill.

Berry said he was worried mid-race on The Offer and likened his racing style to that of Hong Kong Derby winner Designs On Rome.

"He reminds me a bit of Designs On Rome, the horse I ride in Hong Kong," he said.

"He doesn't travel for you but I pulled him out at the 600 metres and asked him to go and within 50 metres he put the race beyond doubt."