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The next great stat

Fans can always sense a game-changing play. Thanks to win probability, they can know for sure.

Updated: December 29, 2010, 11:40 AM ET
By Peter Keating | ESPN The Magazine

Even if you like numbers, you probably think the world needs a Next Great Stat like it needs another Miley Cyrus scandal. When it comes to advanced metrics, we've already got PAP and BABIP, VORP and WARP, wOBA and xFIP ... and that's just for baseball. Isn't enough enough?

No. We're here to tell you that an emerging statistic called Win Probability deserves your full attention. It's elegant, intuitive and revealing. And it will change the way you watch sports.

Win Probability is simply the expected chance that a team will win a game at a particular moment in time, given the situation it faces. A player's contribution to changing a team's odds from one play to the next is called Win Probability Added, or WPA. You remember that crazy Eagles-Giants game in Week 15? The Eagles, after trailing all day, not only climbed back from a 31-10 deficit to tie, but they also forced the Giants to punt from their own 29-yard line with 14 seconds left. At that moment, the Eagles had a 54 percent chance of winning. (We'll explain later how we know that.) Then Matt Dodge lined the ball to DeSean Jackson, who waltzed into the end zone as time expired, bumping Philly's Win Probability to 100 percent. The difference in the Eagles' Win Probability from before the punt to after it, 46 percentage points, represents the WPA of Jackson's return.

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