Shergar Cup officials have revealed that Frankie Dettori, Kieren Fallon and Ryan Moore will all miss this weekend's event due to other commitments.
Dettori had been due to captain the European team at Ascot but as his services are required at Haydock on Saturday, King George-winning jockey Olivier Peslier has been called up to captain the team.
Belgian jockey Christophe Soumillon and Italian Umberto Rispoli have been confirmed as the other two European riders.
Fallon will not captain the Irish team, as originally planned, as he heads to Newmarket, but in-form jockey Richard Hughes, twice winner of the Shergar Cup Silver Saddle, will take his place.
Pat Smullen will join him in the Irish team, with the third rider still to be confirmed.
Hayley Turner will captain the Great Britain team while the fourth and final team, the Rest Of The World, is led by South Africa's Anton Marcus.
Midday going for York glory
Henry Cecil's Nassau Stakes heroine Midday will go in search of further Group One glory in the Darley Yorkshire Oaks on August 19.
The four-year-old secured her third victory at the highest level at Goodwood last Saturday, following on from her success in the race 12 months ago and her glorious display in the Breeders' Cup Filly And Mare Turf.
A trip to York is next on her agenda before defending her Breeders' Cup crown in November.
"I think at the moment Henry would like to go for the Yorkshire Oaks, which is really the natural progression," said racing manager Teddy Grimthorpe.
Wells needing rain: Johnson
Howard Johnson has warned Prospect Wells will not take up his engagement in the totesport Ebor at York later this month unless conditions are suitable.
The former Andre Fabre inmate made a winning debut for current connections in the Pontefract Castle Stakes in June after almost dying following a gelding operation.
But Johnson will not risk him in the famous Knavesmire handicap on August 18 without some give in the ground.
"If it doesn't come up nice ground at York I won't risk him, as I like him a lot," said Johnson.