The women's draw is wide open because of injuries to top players, including second-ranked Victoria Azarenka, a two-time Sony Open champ who won her second Aussie Open this year, but pulled out before her semi at Indian Wells with an ankle injury. No. 5 Li Na hasn't played since injuring her ankle in the Aussie finals, and No. 9 Samantha Stosur (ankle) pulled out last week.

Serena Williams

USA

World ranking/seeding: 1/1 Ht/Wt: 5-10,155 Age: 31

Best finish at Key Biscayne: Champion in 2002-04, 2007-08

Notable: The 15-time Grand Slam champ squeaked by Azarenka to become the oldest No. 1 in WTA history in February. She has been fighting back pain, and as usual, Serena comes to Key Biscayne a tad rusty after bypassing Indian Wells. She's legendary for winning titles after long layoffs.

Maria Sharapova

Russia

World ranking/seed: 3/3 Ht/Wt: 6-2,130 Age: 25

Best finish at Key Biscayne: Finalist in 2005-06, 2011-12

Notable: Coming off a huge comeback year in which she reached nine finals and No. 1 briefly while completing the career Grand Slam with a French Open title, Sharapova also reached back-to-back finals at Indian Wells and Key Biscayne last year. She won Indian Wells on Sunday by downing Caroline Wozniacki.

Agnieszka Radwanska

Poland

World ranking/seed: 4/4 Ht/Wt: 5-8,123 Age: 24

Best finish at Key Biscayne: 2012 champion

Notable: Coming off career year with three titles, including Sony Open, while reaching her first Slam final at Wimbledon, where she lost to Serena. Baseline grinder won two pre-Aussie Open tuneups and with her nemesis Azarenka hobbling (lost eight straight to her) and Williams not match tough (0-4), she could repeat.

Sloane Stephens

USA

World ranking/seed: 17/17 Ht/Wt: 5-7, 135 Age: 19

Best finish at Key Biscayne: 2012 round of 32 loss

Notable: Could this be the Plantation, Fla., native's breakthrough tournament after beating Serena and then nearly upsetting Azarenka in the quarterfinals of the Aussie Open? Stephens hasn't done much since but she has the power and athleticism to pull off a shocker in front of her hometown fans.

Caroline Wozniacki

Denmark

World ranking/seed: 10/10 Ht/Wt: 5-10,128 Age: 22

Best finish at Key Biscayne: 2012 semifinal loss

Notable: Former No. 1 known for her defensive prowess has beefed up her strokes and is coming off a confidence-boosting final appearance at Indian Wells where she lost to Sharapova.

Seeds could change on Monday depending on late withdrawals from tournament

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