Insight-ful ways to beat Serena

Although she still has to win two more matches, Serena Williams is considered the overwhelming favorite to win the 2012 U.S. Open.

Based on the numbers, you can understand why.

Williams has lost a total of 16 games and is the only one of the four semifinalists who has yet to drop a set. She's also a combined 21-3 against the three other players -- Sara Errani, Victoria Azarenka, Maria Sharapova -- left in the semifinals.

However, one year ago, Serena rolled through the semifinals without dropping a set, losing a total of 29 games. It was almost a foregone conclusion that she would beat Samantha Stosur and win a fourth U.S. Open title.

Stosur won the final convincingly 6-2, 6-3.

So what exactly did Stosur do in last year's final that might work as a blueprint for either Errani, Azarenka or Sharapova?

One measure used in the IBM Insights: rallies that end in two or fewer shots. Through the quarterfinals, Serena's five opponents have combined to win 31 percent of those rallies.

In last year's final, Stosur needed to win 52 percent of rallies against Williams that ended in two or fewer shots. Not only did she meet the target number, but she exceeded it considerably in both sets. In the first set, Stosur won 63 percent of those rallies and 65 percent in the second.

Still, it's going to take more than one IBM Insight in order to increase a player's likelihood of beating Serena, especially the way she is serving.

"We identify three IBM Insights for each player before every match, and what is gained on one statistic can just as easily be lost on others," said IBM's Kenneth Jensen, who developed the solution that generates the IBM Insights.

Like Wimbledon, Serena's serve has been the most powerful weapon at this year's U.S. Open. She leads the tournament with 41 aces and percent of first-serve points won at 80.6 (104-129).

In last year's final, Stosur had to win more than 35 percent of first-serve return points to increase her likelihood of beating Williams. Not only is 35 a high percentage of points to win on an opponents first serve, but consider this: Entering last year's final, Serena's opponents had won just 17 percent of the points on her first serve.

So what did Stosur do in last year's final? She won 44 percent of first serve return points in the first set and 35 percent in the second.

Errani, Serena's semifinal opponent, has won 52 percent of the points on her opponents first serve. That's the second-highest percentage in this year's tournament.

But coming even close to that percentage for Errani will be a tall task against Serena, who has lost less than 20 percent (19.4) of the points on her first serve.

Online, the IBM Insights are referred to as "Keys to the Match" and they can be found at U.S. Open Slam Tracker.