By Geoffrey Riddle
Payne, who in 2015 became the first woman to win the Melbourne Cup on 100-1 shot Prince Of Penzance, left a Shergar Cup media event in London on Thursday due to feeling sick.
Doyle, an apprentice who will be allowed to use her 3lb claim on all her rides, remains on standby but judging by reports from Australia overnight it looks unlikely Payne will take part.
The jockey told Australian media that she had caught a stomach bug, and a source told the Sydney Morning Herald just how serious it might be.
"Michelle tried to fight it [the bug], but it was one of those complaints that was everywhere and it really knocked her around," the paper reported.
"She told officials at the press conference that she was unwell, but she doesn't know if they understood. She's back in bed trying to get over it, but it looks doubtful if she can make the races on Saturday."
Payne will have to pass a medical examination at the racecourse on Saturday prior to being permitted to take her five rides.
Doyle has registered 35 successes this season and as Richard Hannon's apprentice has rides booked only at Lingfield's evening meeting she would not miss any engagements.
She would pick up all of Payne's rides, which include Early Morning, who is 4-1 for the Dubai Duty Free Shergar Cup Mile, and Kapstadt, who is around 8-1 for the Dubai Duty Free Shergar Cup Challenge.
Ascot head of communications Nick Smith was upbeat on Friday morning: "Michelle is feeling a little better today, I understand, and hopefully by tomorrow she'll be fighting fit.
"As this is a unique event it made sense to put plans in place, we didn't want to be rushing around in the morning looking for somebody to step in.Hollie Doyle has ridden 74 winners from 631 rides in the past five seasons (Racingfotos)
"Hollie has a ride at Lingfield at 6.10pm but as the last race here is 4pm she won't miss anything."
Kerrin McEvoy, Payne's brother-in-law, also missed the media event at the Sydney Arms in Chelsea, but reportedly walked the course on Thursday afternoon.
British racegoers might be unfamiliar with some of the jockeys taking part in the Shergar Cup at Ascot on Saturday - but the Rest of the World captain.
The 36-year-old Australian came to prominence in Britain when second jockey to Frankie Dettori for Godolphin for four years, before returning home in 2008 to ride as Sheikh Mohammed's main man.
His time in Europe was successful - he made many friends, some of whom he keeps in touch to this day - and his skill in the saddle earned rave reviews.
A Classic success in the St Leger aboard Rule Of Law and victory for Shamardal in the St James's Palace Stakes were the highlights here, but back home he has won two Melbourne Cups (Brew in 2000 and Almandin last year).
"It's always enjoyable to come back to England, I had some great years here," McEvoy said.
"I've ridden in the Shergar Cup once before (2015) so I know what to expect now, but this year there's a bit more on it with my sister-in-law Michelle riding in it - there's a fair bit of rivalry.
"I still keep an eye on what is going on here, especially the big races, so it's not all new.
"I keep in touch with Jamie Spencer, Frankie and Johnny Murtagh still, so with Jamie also riding this weekend there'll be plenty of wisecracks - there always is with him around.
"I really enjoy being back and I'm looking forward to it."
McEvoy is not a regular in team events such as this, but he does enjoy a rare foray into something different, even if the end game is all about winning.
He said: "You don't really have team-talks, as such.
"I know you're in a team and your points add up together, but at the end of the day each race can only have one winner.
"It's still every man or woman for themselves and what you've got to remember is that there's good prize-money on offer for the connections of the horses and we couldn't have events like this without the owners."
McEvoy's Royal Ascot win with Shamardal came when the meeting was staged at York due to the redevelopment in 2005 and he is impressed with what has been done to the place.
"It's some spot now," said McEvoy.
"This day has a nice feel to it, a completely different atmosphere to the Royal meeting in June.
"But it's a big crowd - a different crowd and one that comes to enjoy the day - and there's all sorts going on after racing for them.
"Riding Ascot is great but there is a knack to it and I might not be telling Michelle everything!
"She was here earlier in the summer to ride Kaspersky in the Queen Anne, but that was on the straight course and the round course takes some knowing.
"In all seriousness, though, it does help to know it and there's a stiff climb at the finish. It's nothing like we have at home.
"I look to have a few chances according to the bookies and my best ride appears to be Contango in the Classic.
"Andrew Balding knows how to train a stayer, he won well last time out and is unbeaten."
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