Wozniacki was ahead 7-6(1), 4-3 when Peng was unable to continue. It was an extremely unfortunate ending to a match that Wozniacki had carefully crafted with simple, yet brilliant patterns of play.
Wozniacki's primary strategy was to direct traffic as much as possible to the deuce court to Peng's comparatively weaker forehand wing. When Peng did get to hit a backhand, Wozniacki did everything she could to get it out of her strike zone and not let her step into the ball where she is so dangerous.
Peng hit 230 forehands and only 131 backhands for the match, representing almost two out of three groundstrokes. This created the advantage Wozniacki was searching for in their baseline exchanges. Peng finished with three forehand winners and 32 forehand errors, 19 of which were unforced. By comparison, Wozniacki hit four forehand winners and only made 14 forehand errors, only five of which were unforced.
What's interesting is that Wozniacki also has a more potent backhand than forehand, but Peng's backhand is better. So she simply took her opponent's weapon off the table by hardly letting her hit it, and even then, mostly on her terms.
Peng crushed 12 backhand winners to Wozniacki's five so you can just imagine the carnage it would have done had Peng hit two out of three groundstrokes as a backhand for the match. Wozniacki was smart enough to know that her strength was trumped, and she had to find another way to get the job done.
Wozniacki won 10 more baseline points than her Chinese opponent (75 to 65), and having less than half the forehand errors (14 to 31) was the real area of separation.
The first set tiebreaker was the perfect example of the inner workings of Wozniacki's clever plan.
Peng won the first point courtesy of a crushing crosscourt backhand - the exact thing that Wozniacki was trying to avoid at all costs.
On the second point, Wozniacki went down the line with her first three backhands, hammering away at Peng's forehand. Peng then did get to hit two backhands, but well behind the baseline where she could not hurt Wozniacki. Wozniacki then took all the power out of the point with high, loopy balls to the forehand - because Peng craves a low, hard rally. With Peng always expecting the ball to her forehand, Wozniacki switched to her secondary tactic and ripped hard to Peng's backhand and ultimately finished the point at the net.
At 1-1, Wozniacki went twice to Peng's forehand and then huge to the backhand as a surprise, forcing an error.
At 2-1, Wozniacki made Peng hit five forehands out of seven shots and Peng made a forehand error going down the line - a shot that's out of her comfort zone. Out of the next four points, Peng would make three forehand errors as Wozniacki stayed true to be game plan when it mattered the most to run away with the first set tiebreaker, winning seven consecutive points.
Wozniacki made the most of every break point opportunity in the match, going 4/4, while Peng went 3/9. Wozniacki has only lost her serve 10 times in the tournament so far, winning a healthy 71% of her first serve points, helped by 21 aces.
In her run to the final, she has hit 26 forehand winners and 35 backhand winners. Even though Wozniacki likes her backhand better, she cleverly understands that it's more important in tennis to hit the ball where your opponent doesn't like it than where you want to hit it.
Craig O'Shannessy (@BrainGameTennis) is the leading analyst for wtatennis.com throughout the 2014 season, utilizing SAP Data & Insights to uncover the patterns and percentages that dominate the game. Visit Craig's website at www.braingametennis.com for more expert strategy analysis.