The Hong Kong Mile will be a defining race for French mare Moonlight Cloud who came closer than any other horse to inflicting defeat on Black Caviar.

Moonlight Cloud got to within a head of the now-retired Black Caviar in last year's Diamond Jubilee Stakes at Royal Ascot and has gone on to establish herself as a champion in her own right.

The winner of seven Group One races, Moonlight Cloud is likely to make her farewell in Sunday's feature at Sha Tin, although trainer Freddie Head is hoping it is not the case.

"This could be her last race," Head said.

"Her future hangs on Sunday's race. As a trainer, I'd love to have her another season but the decision is up to George Strawbridge, who bred and owns her.

"You don't want her to race one time too many."

Moonlight Cloud ran one of her worst races when unplaced in the 2012 Breeders' Cup and Strawbridge opted not to try again.

"George Strawbridge decided to send her here rather than another tilt at the Breeders' Cup because he figured she would be better off on this racecourse," Head said.

"The mare has developed year after year since she arrived at my yard but never as much as last winter oddly enough."

The mare pleased Head with her work over 800m on Friday morning.

"I am very happy especially as she seems really happy," he said.

"She's a clever mare and she's saving herself. Of course there remains a question mark over the travelling as she ran badly the only time she travelled before - to Santa Anita - and we won't know for sure about that until Sunday."

Moonlight Cloud will start from gate six while Linton, Australia's lone representative at the meeting, has barrier three.

The Mile will be Linton's final start for trainer John Sadler and Malua Racing with the gelding heading to Dubai, the home of one of his part owners, including ex-pat Australian Martin Talty.

Stable manager Troy Corstens said Linton was close to his best after losing weight on the trip from Australia.

"I'd say he's close to spot-on and now it's just a question of whether he's good enough," he said.

"The horse has well and truly recovered from the slight setback which forced us to scratch him during Melbourne Cup week and this has been his target race since he came back into work so it's not an afterthought."