Peng Shuai of China returns a shot during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Yin Bogu)

Peng Shuai of China signs autographs for fans after the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Yin Bogu)

Peng Shuai of China celebrates during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Yin Bogu)

Lucie Safarova of the Czech Republic returns a shot during the women's singles fourth round match against Peng Shuai of China at the 2014 US Open in New York, the United States, Aug. 31, 2014. Lucie Safarova lost 0-2.(Xinhua/Yin Bogu)

Peng Shuai of China celebrates during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Yin Bogu)

Lucie Safarova of the Czech Republic returns a shot during the women's singles fourth round match against Peng Shuai of China at the 2014 US Open in New York, the United States, Aug. 31, 2014. Lucie Safarova lost 0-2.(Xinhua/Yin Bogu)

Lucie Safarova of the Czech Republic returns a shot during the women's singles fourth round match against Peng Shuai of China at the 2014 US Open in New York, the United States, Aug. 31, 2014. Lucie Safarova lost 0-2.(Xinhua/Yin Bogu)

Peng Shuai of China returns a shot during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Yin Bogu)

Lucie Safarova of the Czech Republic returns a shot during the women's singles fourth round match against Peng Shuai of China at the 2014 US Open in New York, the United States, Aug. 31, 2014. Lucie Safarova lost 0-2.(Xinhua/Yin Bogu)

Lucie Safarova of the Czech Republic returns a shot during the women's singles fourth round match against Peng Shuai of China at the 2014 US Open in New York, the United States, Aug. 31, 2014. Lucie Safarova lost 0-2.(Xinhua/Yin Bogu)

This combo shows Peng Shuai of China(R) and Lucie Safarova of the Czech Republic(L) return shots during the women's singles fourth round match at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

This multi-exposure photo shows Peng Shuai of China serves during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

This combo shows Peng Shuai of China(Top) serves and Lucie Safarova of the Czech Republic(Below) returns a shot during the women's singles fourth round match at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

This multi-exposure photo shows Peng Shuai of China serves during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

Peng Shuai of China returns a shot during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

Peng Shuai of China celebrates during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

This multi-exposure photo shows Peng Shuai of China serves during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

Peng Shuai of China returns a shot during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)

Peng Shuai of China celebrates during the women's singles fourth round match against Lucie Safarova of the Czech Republic at the 2014 US Open in New York, the United States, Aug. 31, 2014. Peng Shuai won 2-0.(Xinhua/Wang Lei)