World number ones Novak Djokovic and Serena Williams head the fields at the Miami Masters hardcourt event that begins on Tuesday, although several big names will be missing. Rafael Nadal, who secured the Indian Wells title on Sunday for his third title since his comeback from nagging knee injuries, and Swiss World No. 2 Roger Federer are absent on the men's side, which features 45 of the world's 50 top players. Injured World No. 10 Samantha Stosur of Australia is missing on the women's side, having suffered a right calf injury that forced her to drop out of her quarter-final at Indian Wells. Djokovic will try to claim his fourth Miami title while Williams attempts to take her sixth career crown at the $8.5 million tournament, which provides first-round byes to seeded players. Williams will play her first event since reclaiming the World No. 1 ranking at Dubai, where she reached the final. Serbian star Djokovic lost to Argentina's Juan Martin del Potro in the Indian Wells semi-finals, ending his 22-match winning streak in a run that included a fourth Australian Open title, his sixth career Grand Slam crown. "I need a few days off and I'll move on to Miami," said Djokovic, who could become the first player since Andre Agassi in 2003 to lift a third Miami title in a row. Del Potro, who also ousted World No. 2 Andy Murray of Britain in the Indian Wells quarter-finals, is looking for big things at Miami as well after falling to Nadal in the Indian Wells final. "After tomorrow I will be happy for this tournament and get motivation for the future, for the next one, and be ready, waiting for another chance like I made in this tournament," Del Potro said. "I'm excited to play Miami. Many Argentinian fans, friends, family, come to watch me there. It's a very good tournament. I'm so excited to be playing there. But first I need a couple of days for recovery, for rest, and I wish to do a similar tournament there." Djokovic won at Miami in 2007 as well as the past two years and has reached the final in four of the past six years. He will play his opener Friday against either Gilles Muller or Lukas Rosol and could face 30th seed Feliciano Lopez of Spain in the third round. Reigning US Open and Olympic champion Murray, who lost to Djokovic in last year's Miami final, will try to add to his 2009 title, which came with a victory over Djokovic. Australian Bernard Tomic or a qualifier will await Murray in his first match. Spanish third seed David Ferrer, in Djokovic's half of the draw, looks to bounce back from a second-round defeat at Indian Wells. He will open against a qualifier but del Potro could be a quarter-final opponent for Ferrer. The South American will open against against either Tobias Kamke or Blaz Kavcic. Czech fourth seed Tomas Berdych, who could meet Murray in a semi-final, will open against either Daniel Gimeno-Traver or Denis Istomin. On the women's side, Williams has a trophy haul that includes Miami titles in 2002, 2003, 2004, 2007 and 2008. The 31-year-old American also reached the final in 1999 and 2009 and she could become the first six-time Miami winner. The 15-time Grand Slam champion is looking to sustain the 2012 form that brought seven titles, including the US Open, Wimbledon and the London Olympics. Williams will open against either Flavia Pennetta or Johanna Larsson on Thursday. Indian Wells runner-up Caroline Wozniacki is a possible quarter-final opponent for Williams, provided the Danish ninth seed escapes a fourth round that could see her face China's Li Na. Li is battling back after an ankle injury suffered in losing the Australian Open final. Defending champion and fourth seed Agnieszka Radwanska of Poland could meet Venus Williams or Sloane Stephens in the fourth round. World No. 3 Victoria Azarenka and Indian Wells champion Maria Sharapova are on a semi-final collision course. Four-time Grand Slam champion Sharapova will open against wither Canadian wild card Eugenie Bouchard or a qualifier.  Source : AFP