Wozniacki through to U.S. Open final after Peng forced to retire due to heat stroke

Well it's not exactly the way you would've liked to see it happen, but Caroline Wozniacki is back in a Grand Slam final for the first time in five years. 

The 10th-seeded Dane, enjoying a surprise late-2014 renaissance, was leading unseeded Peng Shuai 7-6, 4-3 in Friday's U.S. Open semifinal, when Peng was overcome by a bout of severe cramps, which were later revealed to be related to heat stroke. The temperature during the match hovered around 85 degrees. 

After taking a 10-minute injury timeout, Peng returned, making a game attempt to gut out the match. But the pain was too much. She collapsed after six points and was forced to retire, eventually needing a wheelchair to cart her off the court. 

The heat seemed to distress both players for much of the match, but the quality of tennis remained high through the first set and a half. The two players showcased similar games, with excellent court coverage, strong backhands, a good deal of variety and tremendous consistency.

The result was a series of long, probing, hypnotic baseline exchanges. Wozniacki prevailed in most of the extended rallies, finding success in attacking Peng's forehand, a gawky and inconsistent two-hander. But she also struggled with her serve, gifting Peng 10 free points via double faults.   

Peng had her chances. She broke Wozniacki three times in the match, including a game that put her up 6-5 with a chance to serve out the first set. But she couldn't consolidate any of those breaks, as Wozniacki answered all three with breaks of her own. Peng came into the match having held 40 straight service games, and having been broken just three times all tournament. Wozniacki broke her four times, and didn't squander a single break point.  

Peng was down a break in the second set when the cramps hit. What started out looking like a dull, lingering pain, quickly turned into a writhing agony that was difficult to watch. As she sobbed on the court, a concerned Wozniacki came over to try and offer some comfort, a tender show of empathy and sportsmanship that  drew a wave of cheers from the Arthur Ashe crowd. 

When it became clear Peng wouldn't be able to finish, the match was called, and Wozniacki was officially a two-time U.S. Open finalist. Her celebration, if you can call it that, was appropriately muted. 

With the bittersweet win, Wozniacki moves on to the final, just her second at a Slam. Her first also also came at Flushing Meadows, in 2009, and ended with a straight-sets loss to Kim Clijsters. 

In the final, Wozniacki will face her good friend Serena Williams, who she's played tough recently, but against whom she owns a 1-8 lifetime record.