The former world No. 1, the event's 16th seed, was due to face top-seeded Maria Sharapova, but a fever that started Friday got worse.
"I am very disappointed to not be able to take to the court today," Davenport said in a statement. "Right after my quarterfinal victory, I started feeling sick while receiving treatment from the primary healthcare provider. I returned to my hotel where the tournament doctor came to see me. Unfortunately, I was running a fever and had aches, pains and a headache. Those symptoms worsened today and I am so sorry to the fans and people involved in the tournament."
Davenport's withdrawal means Sharapova advanced to Sunday's final in a walkover to face Slovakian Dominika Cibulkova, 18, who will be playing in her first tour final.
Cibulkova beat Alize Cornet of France 6-2, 2-6, 6-4 in Saturday's other semifinal match.
Sunday's winner will earn $95,500.