World number one Caroline Wozniacki secured her third tournament victory of the year at the Family Circle Cup.
The Dane, who also won at Dubai and Indian Wells, beat Russia's Elena Vesnina 6-2 6-3 in Charleston.
Although she was forced to work hard, Wozniacki was solid from the baseline and made just 10 unforced errors.
Meanwhile, Victoria Azarenka beat Romanian qualifier Irina-Camelia Begu to win the final of the Andalucian Tennis Experience in Marbella.
Wozniacki had break points in every game in the second set as she moved towards her 15th career title - from 23 finals - at the age of 20.
The defeat is the fifth in as many finals for unseeded Vesnina, who was also beaten by Wozniacki when they met in the New Haven final in 2009.
Her only glimmer of hope came at 3-3 in the second set when she had two break points but Wozniacki once again lifted her game when it mattered and held on.
Wozniacki, yet to win one of the four major tournaments, said afterwards: "I feel confident and I know I can win a Slam. It's all about getting everything together. The draw has to fit, I have to play well for two weeks, things like that all have to work together."
Wozniacki saved all four break points she faced against 56th-ranked Vesnina, who commented: "Sometimes you feel like she's everywhere on the court. She uses pace, she uses the whole court and she's playing smart tennis."
In Spain, Azarenka's victory gave her a second straight tournament success after Miami last week.
Begu had never won a main-draw match on the WTA Tour before this event but beat second seed Svetlana Kuznetsova in Saturday's semi-final.
However Belarusian Azarenka, ranked sixth in the world before the tournament, had too much ammunition in the final, winning 6-3 6-2. She broke Begu's serve four times in the first set and three times in the second on her way to a victory which takes her into the world's top five.