The Caulfield Cup has eluded Glen Boss but the jockey reckons it's only a matter of time before that changes.

Boss has won the other three races considered `majors' in Australian racing - the Melbourne Cup, Cox Plate and Golden Slipper - but needs a Caulfield Cup to become the eighth jockey to have won all four races.

"Everyone wants to talk about it. It doesn't bother me," Boss said.

"It'll happen. It's not if, (but) when. It might be Saturday."

Mick Dittman, Roy Higgins, Damien Oliver, Chris Munce, Neville Sellwood, Pat Hyland and Jim Cassidy have won all four races.

Boss rides the Chris Waller-trained Royal Descent in Saturday's $3 million 2400m handicap and will have to overcome the widest barrier in the capacity field.

But Boss said he didn't see that as a problem for the mare and believes the six-year-old has the form to suggest she can run a big race with 53.5kg.

"She's an easy horse to ride. She's got good gate speed, she'll probably roll forward, she'll slot in somewhere," Boss said.

"So she would be doing the same thing from the inside anyway. I'd be kicking up to hold my spot anyway. It doesn't faze me," Boss said of the draw."

Boss rode Royal Descent when a last-start second to stablemate Preferment in the Turnbull Stakes and he believes her form is as good as any horse going into the race.

"I know she's been getting beaten but she was terrific the other day and essentially got beaten by a horse that could probably nearly win a Cox Plate or nearly win the Melbourne Cup," he said.

"She's got form behind Kermadec. That's as solid as you can get."

The closest Boss has been to winning a Caulfield Cup was his second on Makybe Diva to Elvstroem in 2004.

Boss has three Melbourne Cup wins on Makybe Diva, three Cox Plate wins (Makybe Diva, So You Think and Ocean Park) and two Golden Slippers (Flying Spur and Sebring) on his CV.

"It would be nice - it's a Caulfield Cup," Boss said.

"To get the full lot (of majors).

"If it happens it happens. I never worry about that stuff.

"I'll just go out there and give her my very best ride."