Being down 0-40 on your serve presents both peril and opportunity.
If you can get out of that game, you take a lot of momentum with it, and history shows these moments in a match are often the exact times where victory actually slips right between your fingers.
Stosur had broken in Kvitova's previous service game at 5-6 to clinch the second set, and was enjoying her most commanding period of the match.
Stosur held her opening service game of the third set to love and had won seven consecutive points to have Kvitova faltering at 0-1, 0-40. Kvitova had committed four forehand errors and two backhand errors to start the third set and Stosur was just a shot away from taking real control of the match.
Kvitova was having trouble finding the court and instead of applying pressure with consistency and shot tolerance, Stosur committed four quick errors, and her moment to shine quickly evaporated.
Stosur shanked a backhand return error wide, and then made a first-shot forehand error after her return on the next two points and all of a sudden it was deuce. Stosur then made a forehand return error and Kvitova won her fifth straight point with an ace down the middle.
Opportunity had come and gone in an instant for the Aussie.
Stosur was particularly wasteful of her break point chances throughout the match, only winning 18% (3/16), including 2/4 in the first set, 1/8 in second and 0/4 in the third set.
It was not a particularly high level of play from either player, as Kvitova amassed 39 unforced errors to Stosur's 36.
The main problem for Stosur was getting deep enough into a point to move Kvitova wide off the court to force errors. The Australian's forehand broke down time and time again early in the point, which robbed her of employing her winning strategy.
Stosur's forehand was good for six winners for the match, but misfired for 31 groundstroke errors and five return errors. A major concern was that 64% (20/31) of Stosur's forehand groundstroke errors occurred as the very first shot after either a serve or a return. She was her own worst enemy.
This gave Kvitova a huge pool of early errors to rely on, and stopped Stosur from applying pressure with a stretching strategy later in the point to secure victory.
Stosur's backhand was more solid once the rally began, regularly mixing in some slow, low slices to get the ball out of Kvitova's strike zone. Stosur's backhand was the main reason she broke serve at 5-6 in the second set with two powerful winners down the line and three total for the match, but it was a clear liability returning the lefty serve.
You rarely see more return errors than rally errors from a forehand or backhand, but Stosur committed 19 return errors and only 17 rally errors for the match - totaling a troublesome 42 forehand and backhand errors within the first two shots of points for the match.
Kvitova will play Maria Sharapova in Sunday's final and will move to No.2 in the world if she can win that match.
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.