Serena has surgery on her big toes
A medical certificate from Florida podiatrist Jeffrey Rockefeller says Williams "was treated for a chronic foot disorder which involved minor procedures on both of her great toes."
He said she needs to minimize activity to fully recover.
Williams, the WTA player of the year after winning Wimbledon, the U.S. Open and London Olympics, was replaced by Li Na for the exhibition on Dec. 29 in Hua Hin.
Copyright 2012 by The Associated Press