Donald was forced to abandon his final round at the US Open
Luke Donald is waiting to find out what is wrong with the injured wrist which forced him to pull out of the US Open midway through Sunday's final round.
The 30-year-old was due again to visit a doctor in Chicago on Wednesday.
Donald has already pulled out of this week's BMW International Open and may miss the French Open next week.
Asked if he could miss next month's Open his agent Rob Alter told the BBC: "We don't know what the situation is - we're taking it one day at a time."
Alter understands the wrist is badly sprained but an MRI scan has failed to reveal the exact nature of the problem.
"Hopefully it will respond to rest. How long a rest though, is the question," said Alter.
Donald, who has seen a doctor every day since the injury, is eighth on the Ryder Cup points list and 31st on the European table.
He needs to be in the world top five or Europe's top five to qualify automatically for the match against the United States in September.