The Godolphin stable admitted Frankie Dettori's mount Mamool was lame as he finished last in the Melbourne Cup. Mamool was favourite for Australia's premier race but was overtaken by the field in the home straight.
"The vets have examined Mamool and found him to be lame in the right hind leg," said Godolphin trainer Saeed bin Suroor.
"We will assess the extent of his injury over the next 24 hours but that was not his true running."
Bin Suroor added: "I had a talk with Millstreet's jockey Patrick Payne and he felt the pace was not excessive and the horse was comfortable.
"But when he asked to pick up in the straight there was nothing there.
"I was disappointed really with both horses. We expected better than this. The horses before the race were sound, happy, healthy and nothing wrong with them."
Australian horse Makybe Diva, a 7-1 shot, won the race for trainer David Hall, with She's Archie second.
The British-trained outsider Jardines Lookout, with Darryll Holland in the saddle, finished third.
Trainer Alan Jarvis brought Jardines Lookout back to Australia after the gelding's seventh place last year.
And he was confident that his horse was stronger this time round, despite a serious injury in a stalls accident in his first run this season at York.
"I thought they went plenty quick enough and I knew they wouldn't keep it up for two miles at that speed," said Jarvis.
"He's a great finisher. I know what he can do, I've seen him do it before so I knew he had got a chance.
"I knew he would be picking them off at the end, which he did. We could have done with another couple of furlongs."
Jardines Lookout's jockey Darryll Holland, riding in his first Melbourne Cup, told BBC Radio Five Live: "They just seemed to kick away from me a bit.
"I knew my horse would stay right to the line and that's why I kept at him and he just nicked third.
"It's great for the connections. It's great for me on my first ride in it and I'd like to come back and go two places better.
"But to come here and have 120,000 people shouting at you, it really is a great occasion."