Andy Murray has a tear in his elbow, according to his older brother, Jamie.
The world No. 1 withdrew from Miami with an elbow injury.
"It's some sort of tear," Jamie, the world No. 7 in doubles, told British reporters in Miami. "He said he can do everything except serve, and he told me rest was all he had to do."
Murray, who had shingles following the Australian Open, also had the flu for a few days following his withdrawal, added Jamie.
The injury means Andy is unlikely to play the Davis Cup quarterfinal against France next week.
“The most important thing for him is just to get healthy,” Jamie said, “because he has had a few issues now."