China's Peng Shuai cramped up due to heat at the U.S. Open on Friday leaving her match against Caroline Wozniacki in the second set. Wozniacki was awarded the victory advancing to her second Open finals at Flushing Meadow's Arthur Ashe Stadium against Serena Williams.

Both players started out strong as they broke each other's serves and finish the set with a tie-break which Wozniacki won 7-1.

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In the second set, Wozniacki broke Shuai's serve early to edge out 2-0, but the 28-year-old Chinese woman quickly broke back the Danish to tie the match at 2-all.

Wozniacki, 24, was unfazed as she marched to another break to go up 4-2, but Shuai answered back with her serve and put the ball on Wozniacki's side.

While Wozniacki was serving and double faulted for the 9th time, Shuai was cramping up and required medical attention.

After 10 minutes, the courageous Shuai went back on court but after a 10th double fault from Wozniacki and a winner down the line, Shuai cramped up again and could not continue. She was forced to retire the match 7(7)-6(1) 4-3 in a match that lasted just over two hours.

At 82 degrees and humidity at 77 percent, the heat got the better of Shuai as her body temperature rose and her whole body started to cramp up.

"I just try to fight, and my body is getting more and more hot and it start cramping," Shuad said. "It's really painful right there."

When Shuai returned after a 10 minute medical timeout she made a winner down the line but then collapsed which had Wozniacki worried.

"When she came back and still played she made a winner down the line on my return, I was like, maybe she's going to be fine," Wozniacki said. "I wanted to go over and make sure she was okay. I know that she's had heart surgery when she was 13."

Despite Shuai's retirement of the match, the Chinese woman is such a great person that even World No. 1 Serena Williams was saddened about the news.

"I was really, really saddened by it," Williams said. "She's such a great person. I'm just hoping she's better."

The last two times that Wozniacki and Williams fought was two tough three-set matches and promises to be an exciting final match. Williams is 8-1 lifetime against Wozniacki.

TagsPeng Shuai, Caroline Wozniacki, serena williams, tennis, Sports