During the second set,Williams called for her trainer with the score 5-4 and on serve. it appears she hurt her lower back while attempting to pull up short during the eighth game of the second set.
Stephens took control when she broke Williams serve after the injury. Williams later lost her cool in the third set, smashing her racket onto the court and tossing it at her chair.
The No. 25 player in the world, Sloane Stephens will attempt to dethrone defending champion Victoria Azarenka in the semifinals. By Steve Kish