TAB Sportsbet has released a market on Black Caviar's winning margin at Morphettville on Saturday.

Black Caviar hasn't raced since winning the Coolmore Lightning Stakes at Flemington on February 18 by 1.8 lengths.

She is expected to put a bigger space in the opposition this weekend over 1200 metres.

“Black Caviar is not a betting proposition for most punters so this is just another way to get involved,” said TAB Sportsbet's Matt Jenkins.

In other feature racing at Morphettville, Empress Rock has firmed from $4.50 into $4 to win the Schweppes Oaks.

Black Caviar winning margin – Saturday April 28

$1.90 – 4 lengths or more

$1.90 – Less than 4 lengths

* Not available in NSW