Safina and Ivanovic in early Miami exits

(CNN) -- Second seed Dinara Safina saw her chances of taking over from Serena Williams as world number one shattered by a straight sets defeat to Australian Samantha Stosur at the Sony Ericsson Open in Miami.

Safina, who could have overtaken Williams with victory at Key Biscayne, went down 6-1 6-4 to Stosur in their third round match on Sunday.

Safina reached her career-high ranking after reaching the final of the Australian Open where she was beaten by Serena, who is top seed in Florida.

The shocks in the WTA tournament did not end there as seventh seed Ana Ivanovic also crashed out.

The French Open champion was beaten 6-4 4-6 6-1 by Agnes Szavay of Hungary, following her Serbian compatriot and third seed Jelena Jankovic out of the tournament.

But fourth seed Elena Dementieva of Russia made the last 16 by seeing off 31st seed Carla Suarez Navarro of Spain 6-2 6-2.

Former U.S. Open champion Svetlana Kuznetsova of Russia is also safely through after beating Nicole Vaidisova 6-1 6-4.

In the men's tournament home hope Andy Roddick beat Russian Dmitry Tursunov 7-6 6-2 to reach the fourth round and continue his fine form in 2009.

Qualifier Taylor Dent became the second American to reach the last 16 when he upset 15th seed Tommy Robredo of Spain 7-5 6-3 in other early action on Sunday.