In Secret's autumn campaign is up in the air after Saturday week's Group 1 Black Caviar Lightning was ruled out for the four-year-old.

The daughter of I Am Invincible was being set for a first-up clash with Imperatriz and Private Eye in the Flemington feature, but will miss the 1000-metre weight-for-age event after failing to satisfy trainer James Cummings at trackwork during the week.

"Stable have advised after performing below expectations at trackwork, the mare will bypass the Lightning," Racing Victoria announced via social media on Thursday afternoon.

In Secret owned the second line of Black Caviar Lightning betting behind eight-time Group 1 winner Imperatriz at the time of her withdrawal.

The $1 million race will be run at her favourite track, where she won the 2022 Coolmore Stud Stakes and last year's Newmarket Handicap.

Imperatriz, who has also been in the headlines this week after a plain trial at Cranbourne on Monday, is back into odds-on favouritism with Private Eye the new second elect from I Am Unstoppable and Bella Nipotina.