Happy Clapper's trainer Pat Webster has never before had a horse good enough to run in a Cox Plate, and doubts he will again.

But in Happy Clapper, the Randwick trainer has one he believes is a top four chance in Saturday's $3 million race at Moonee Valley.

Happy Clapper and Awesome Rock are the only non-Group One winners in the field of 10 for Saturday's weight-for-age showpiece but Webster points to the gelding's Queen Elizabeth Stakes performance as a reason for optimism.

"He's only had one run over 2000 metres in a weight-for-age race which was a $4 million race. He ran third and probably should have run second. So why not have a go?" Webster said.

Happy Clapper was the second horse onto the track at Tuesday's trackwork session at Moonee Valley, the gelding's first look around the unique Melbourne racetrack.

"I said to Chris Waller 'what's the drill here?' He said 'just follow Winx out'. I said 'we've been doing that a bit'," Webster said.

Happy Clapper finished fifth to Winx in the George Ryder Stakes in the autumn before running second to the star mare in the Doncaster Mile.

Winx is odds-on favourite to win her second Cox Plate.

A week after Happy Clapper's Doncaster placing he finished third in the Queen Elizabeth Stakes won by another Cox Plate rival Lucia Valentina.

His spring campaign has included a last-start fourth in the Epsom Handicap (1600m).

"I'd like to think he'll be top four," Webster said.

"I can't see why not. The other two, Winx and Hartnell, seem to have it to themselves but like I said, he's only had the one go at 2000 in the Queen Elizabeth and he should have run second, so I can't see why he shouldn't be top four.

"In the Epsom I tried to keep him a little bit fresh because I thought he was looking for 2000, and he hit the line like he needed 2000 metres. And he'll have winkers on on Saturday."

Webster has been involved in racing for decades and is excited to have a Cox Plate runner.

"It will be our first and only one I reckon," he said.

"I've never even had anything to even nominate."

Six-year-old Happy Clapper has won six of his 19 starts and earned more than $1.35 million prize money.

"We only keep eight (horses), so you just don't get horses like him," he said.

"But we've had him since he was a pup. He's special. They become family when you've got a small stable. So it's been good for everybody."