CHARLESTON, S.C. -- Venus Williams has advanced at the Family Circle Cup, battling from behind to defeat Chanelle Scheepers 7-5, 7-5.

It was another long day Wednesday for Williams, ranked No. 28 in the world and who needed an hour and 50 minutes to finish the straight-set victory over the South African. Williams fell behind 3-1 in the first set and trailed 4-1 in the second.

The seven-time Grand Slam champion has battled injuries and Sjogren's syndrome, a fatigue-causing autoimmune disease, during the past two years. She was on the green clay in Charleston for two hours and 15 minutes on Tuesday in a three-set victory.

Earlier Wednesday, American Sloane Stephens was upset 6-4, 6-4 by Elina Svitolina of the Ukraine, who got her fourth career victory over a top 20 player.