The weather and the absence of champion Winx has contributed to a fall in attendance numbers to watch Lys Gracieux win the Cox Plate at The Valley.

Moonee Valley posted a crowd of 24,648 the first Cox Plate post-Winx when more than 38,000 turned up to see the champion win her fourth successive Cox Plate last year.

Also absent was Daryl Braithwaite singing the Cox Plate anthem The Horses, replaced by a group of 99 people, from a number on Melbourne choirs.

Moonee Valley Racing Club chief executive Michael Browell said it was going to be hard to replicate those attendance figures, especially from the past two years.

"The weather hasn't been on our side and we always knew it was going to be hard to come back after Winx-three and Winx-four," Browell said.

"But all those that have been here today have seen something special."

With Winx retired, Browell said it was important for the club to lure a big name to The Valley.

"She's one of the highest-rated horses in Japan, she's one of the best performed and is a true international Group One horse and we saw a true Group One performance today," Browell said.

Unless there is a rule change, Browell doubts Lys Graxieux will return to Melbourne to defend her Cox Plate crown.

"She's a syndicate horse in Japan and I think the syndicate rules have it that horses have to be retired at six," Browell said.

"Unless they can change those rules, she'll be in the breeding barn.

"Now that we've got this relationship with Northern Farm, they're one of the biggest racing ventures in the world, they now know the type of horse they need to bring down to win the Cox Plate, so hopefully they'll be back."