The 21-year-old Serb reached the top of the WTA rankings after winning last year's French Open. But it's been a struggle since, with a thumb injury, early Grand Slam exits and a series of puzzling losses hastening her decline to No. 8. The latest complication is a knee injury suffered in April during her country's Fed Cup win over Spain -- but she insists she's fit to defend her crown.
Text: Bryan Armen Graham/SI.com
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