Li Na of China waves to fans after winning the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China returns the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China shakes hand with Bethanie Mattek-Sands of the United States after winning the semi-final match of Porsche Tennis Grand Prix in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China returns the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China returns the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China signs for fans after winning the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China returns the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China reacts during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China serves the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China kicks the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Jiang Shan (2nd R), husband of Li Na, watches Li Na's semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China serves the ball during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China attends a news conference after winning the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Li Na of China reacts during the semi-final match of Porsche Tennis Grand Prix against Bethanie Mattek-Sands of the United States in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)

Bethanie Mattek-Sands of the United States returns the ball during the semi-final match of Porsche Tennis Grand Prix against Li Na of China in Stuttgart, Germany, on April 27, 2013. Li Na won 2-0. (Xinhua/Ma Ning)