Serena Williams thought her ball was long but to her delight , Watson 's challenge showed the ball to be in .
Third time was a charm for Serena Williams when she powered a backhand cross-court that forced a Watson backhand error .
Serena Williams thought Serena Williams ' ball was long but to her delight Watson Watson 's challenge showed the ball to be in .
Third time was a charm for Serena Williams when she powered a backhand cross-court that forced a Watson backhand error .