American Andy Roddick upset third seed Roger Federer 7-6 (7-4) 1-6 6-4 in the third round of the Miami Masters tennis tournament today.
Roddick, who is seeded 31st, will play either Argentina's Juan Monaco or Gael Monfils of France in the fourth round.
Meanwhile, defending champion Novak Djokovic defeated No.27 seed Viktor Troicki 6-3 6-4 in an all-Serb third round matchup at the tournament.
The world No.1 Djokovic, who won Miami titles in 2007 and 2011, saved seven of eight break point opportunities as he beat Troicki for the 11th consecutive time.
Djokovic finished with two aces, one double fault and won 73 per cent of his first-serve points in the 85-minute match.
"Generally I feel that I have been playing well,'' Djokovic said.
"I did have some ups and downs, especially in today's match, but I'm confident that I can raise the level of my performance in every match.''
Djokovic next plays 17th seed Richard Gasquet of France.
On the women's side of the draw, Serena Williams rallied from a break down in both sets to beat Sam Stosur 7-5 6-3 in a rematch of the 2011 US Open final.
Ranked 11th, Williams is playing in her first tournament since January after being sidelined by a left ankle injury.
She hit 20 aces and lost only six points on her first serve, but she had to rally after being broken in the first game of each set against the No.5-ranked Stosur.
Women's top seed Victoria Azarenka survived a scare from 16th seeded Dominika Cibulkova, gutting out a 1-6 7-6 (9-7) 7-5 victory in the fourth round.
Cibulkova made Azarenka, of Belarus, work to protect her season long match win streak which now stands at 26.
"It felt like she closed her eyes and just went for everything, and me, I couldn't really open my eyes,'' Azarenka said.
"It was like I was blinded.
"But my coach came to the court, kicked me a little bit that I have to at least try to change something. It was like a snowball. I kept rolling ... and I didn't really adjust.
"In the end I tried to change something. But it was more about fighting in my heart today.''
Azarenka advances to face France's Marion Bartoli, who easily defeated Maria Kirilenko 6-1 6-2 earlier in the day.
World No. 2 Maria Sharapova defeated fellow Russian Ekaterina Makarova 6-4 7-6 (7-3) to set up a quarter-final clash with China's Li Na.