Tennis players Serena Williams and Novak Djokovic both have the potential to win Grand Slams, one of the rarest achievements in sports. But it's not an easy feat.
The world No. 1 defeated Romania's Monica Niculescu 7-5, 7-5 in the second round. It was her first match at the tournament since her infamous 2001 title victory after which she vowed a boycott.