The tournament announced on Wednesday that second-ranked Dinara Safina and 2008 champion Nikolay Davydenko have also withdrawn.
Sharapova, who won the Memphis title last month, withdrew after an MRI revealed the injury that is expected to sideline her three to six weeks. She last played at Key Biscayne in 2007.
Story continues below ↓advertisement | your ad hereSafina withdrew because of a back injury. Davydenko pulled out because of a broken left wrist.
The 13-day tournament begins Tuesday. The field still includes Roger Federer, Rafael Nadal, Andy Roddick, Serena and Venus Williams, Justine Henin and Kim Clijsters.
© 2010 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.Sharapova to play in Birmingham in JuneMathieu’s season appears over