Mired in a marathon game midway through the opening set, Maria Sharapova wore down her opponent with characteristic resolve and relentlessness, then won the last point without hitting a shot.

That put Sharapova ahead to stay, and she beat fellow Russian Elena Vesnina on a muggy, 85-degree Fahrenheit afternoon at the Sony Open, 6-4, 6-2.The No. 3-seeded Sharapova moved into the fourth round, eager to fill one of the few holes in her resume. While she completed a career Grand Slam last year, she has never won Key Biscayne, losing the finals in 2005, 06, 11 and 12.

Her pivotal moment Sunday against Vesnina came at 3-all in the first set. The next game went to deuce seven times, with Sharapova repeatedly erasing a deficit, until Vesnina dumped a weary second serve into the net on break point.All told, Sharapova benefited from eight double-faults by Vesnina, and erased eight of the nine break points she faced.

Two seeded women were eliminated No. 6 Angelique Kerber and No. 11 Nadia Petrova. Kerber lost to No. 28 Sorana Cirstea 6-4, 6-0, while Petrova was ousted by No. 22 Jelena Jankovic 7-6 (7), 6-4.Lucky loser Lauren Davis of the United States was beaten by No. 32 Alize Cornet, 2-6, 6-3, 6-2.