The owners of 13 worthy thoroughbreds have paid $330 each for the right to think about going along for the ride with Black Caviar on Saturday.

By 10 o'clock on Wednesday they must decide if they want to pay another $5500 to chase her ample backside down the Flemington straight in what will almost certainly be the world champion mare's final run in Melbourne.

For some, it will be worth it just to say they were there.

For most, the $5830 in entry fees will be a reasonable investment, with the first eight across the line to receive a minimum of $10,000 and as much as $90,000.

But there are some risks associated with chasing a horse that has never been caught.

On Saturday at Caulfield some of them were revealed when an inordinate number of horses finished in various states of distress from chasing others who were better than them on a hot afternoon.

The forecast for the Black Caviar Lightning Stakes is for 31 degrees, not a day for extreme exercises in utter futility from horses who will do their best to achieve the impossible.

Saturday's race will be the 23rd in Black Caviar's career and her first since she performed for the Queen last June.

After she wins it for the third successive year she will have earned $7,302,436 and maintained her perfect record.

It will be her 12th Group One win and her eighth victory at Flemington, the scene of her first race which she won by five lengths in April 2009 beating a horse called Kwassa Kwassa.

It will also be the beginning of the end.

Black Caviar will have two more runs, probably in Sydney, the home of Neil Werrett, the man who bought her and shared her with his friends.

Then one of the the greatest racing careers of any Australian racehorse could be over and Black Caviar will let down and prepare to go to stud.

There she will be served by a yet to be determined stallion who won't have a clue who she is.