World number one Serena Williams on Tuesday become the latest high-profile name to pull out of the Qatar Open, citing flu for her withdrawal. It is the latest blow for organisers coming less than a week after Maria Sharapova pulled out of the Doha tournament which starts on February 21 with an arm injury. "I unfortunately have to withdraw from the Qatar Total Open as I have come down with the flu and do not feel 100 percent," said Williams in a statement released through the Qatar Tennis Federation.