Warwick Stakes favourite First Seal will have to match Sunline if she is to make a winning return at weight-for-age at Randwick on Saturday.

Rated one of the greatest racemares of the modern era, Sunline started her four-year-old season with a Warwick Stakes win in 1999.

Sunline went into the race as a Doncaster Handicap winner as a three-year-old.

But history says the significance of Sunline's win over Tie The Knot in the Group Two event shouldn't be understated because four starts later she won the Cox Plate, the first of her three triumphs in Australia's best weight-for-age race.

But since Sunline's victory there has only been one other mare to claim the Warwick Stakes, with that honour going to Private Steer in 2004.

A race that always attracts legitimate spring carnival chances, the Warwick Stakes has been a good one for favourites although notable mares to be beaten into second place include Dizelle (2005), Secret Admirer (2012), Streama (2013) and Royal Descent (2014).

Trainer John Thompson is the first to admit First Seal is no Sunline yet there are similarities in their records at a comparative stage of their careers.

Sunline first came to prominence during the 1998 Sydney spring carnival in winning the Furious Stakes, Tea Rose Stakes and Flight Stakes.

Likewise, First Seal burst into stakes company last year with her Tea Rose win and her Flight Stakes victory.

And Thompson says First Seal shouldn't have to be as good as Sunline to make a successful debut at weight-for-age.

"A lot of good horses in the race are returning and they've all got their eyes on bigger prizes later on," Thompson said.

"But she's probably the horse that has got that brilliant turn of foot that maybe could beat the stayers off first-up."

First Seal is among three mares in the Warwick Stakes with Royal Descent aiming to go one better and Gust Of Wind having her first start since winning the ATC Australian Oaks.

Ironically, Kermadec is rated First Seal's main danger as a Doncaster winner trying to resume with a Warwick Stakes victory in the next season.

It's the same double Private Steer completed in 2004 but one that has since been elusive.