Aidan O'Brien will keep a close check on Starspangledbanner's legs ahead of his intended run in the Breeders' Cup Turf Sprint at Santa Anita on Saturday.
The Irish trainer admitted slight concern about the six-year-old but hoped the problem would be successfully treated.
"Since he arrived here, all four of his legs were a bit humid, which is because he didn't get to do much walking," said the Ballydoyle handler. "We will treat it and hope it disappears quickly."
Starspangledbanner has had four races in the last few months since returning from an unsuccessful stud career. O'Brien was heartened by the Australian bred star's run at Dundalk last week when he was a close fourth in a Listed race.
"We learned very early on that he hates soft ground," he said.
"When he was trained in Australia, he was getting away with being ridden in front and then being slowed down, but you can't do that in America.
"We learned after France (Prix de la Foret), that he's a sprinter who wants a strongly-run six furlongs and this was the only big sprint left for him.
"We made plenty of use of him at Dundalk the other night and he pleased us."