The 19-year-old American defeated the Serbian 6-4 0-6 7-5 despite trailing 3-1 in the third set.

BBC: SPORT | Tennis | Sharapova wins as form improves

And despite trailing 1-0 through an own-goal, the 'Blue Sharks' hit back with two strikes in the final nine minutes to see off Angola.

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Williams has now beaten second-ranked Sharapova in their past 12 meetings, and was in control for most of the match despite trailing 3-1 in the second set.

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