Champion rider Damien Oliver is hoping first impressions are all they seem after his introductory ride on 2010 Melbourne Cup winner Americain on Wednesday.

"He's a lot more impressive when you get on his back than when you look at him," Oliver said.

"He's such a big and imposing horse to look at, but I was really taken by his athleticism."

Oliver won the ride on Americain when connections ran out of patience with French jockey Gerald Mosse whose Melbourne Cup victory on the horse has been followed by a series of questionable rides.

The dissatisfaction reached breaking point in the Caulfield Cup when the horse finished fourth to Dunaden, the same position he filled behind his French compatriot in last year's Melbourne Cup.

Connections diplomatically said they preferred the riding style of Australian jockeys when they announced the switch.

But after Oliver galloped Americain at Werribee on Wednesday, co-owner Gerry Ryan was more to the point.

"You can't win the Melbourne Cup sitting three-wide with 58kg," Ryan said.

"We needed an Australian jockey."

The call-up came at a time when Oliver's career was at a low point following allegations he bet on a rival horse in a race in which he was riding.

But he said he had put that behind him, at least for the next week.

"It's very exciting, a great opportunity," Oliver said.

The two-time Cup winner is also mindful that it is 10 years since he last won the race aboard the Irish horse Media Puzzle.

That win came a week after the death in a riding accident of his jockey brother Jason.

"I don't want to get ahead of myself, but it would be a great anniversary," Oliver said.

Americain worked over 2000m with stablemate Shahwardi at Werribee on Wednesday, finishing off the gallop impressively.

"He's got great acceleration," Oliver said.

"But through the line was the best part of his work, he just wanted to keep going."

Americain had firmed to outright Cup favouritism at $6, thanks largely to Oliver's booking, and was in to $5.50 after his latest gallop.