People sometimes ask me what the single-most useful statistic is in hockey. Obviously if we had a reliable way to measuring how many wins a player contributed to his team, that would be our choice, but the computational complexity of such a measure limits its value to someone who's looking for a simple yet powerful stat.
My vote for the simplest yet most-useful statistic is PDO (the name is short for its inventor, also named PDO.) PDO is nothing more than shooting percentage plus save percentage. But this simple statistic captures several complex and powerful concepts:
1. Shooting percentage is primarily luck-driven
We've gone through this a billion times - a season's worth of shots, whether for a team, while a player's on the ice, or just those taken by an individual player, simply isn't a large enough sample to overcome the role of luck in putting pucks in the net.
2. Save percentage is primarily luck-driven
The spread of goaltending talent is much smaller than most people suspect, and 29-year-old goalies jumping from obscurity to the All-Star game are hardly uncommon. Again, we've got single-season sample size issues, backup goalies, and a whole lot of luck.
3. The apparent talent there is in these quantities, particularly offensive finishing ability, shows up as negative talent at the other end of the ice
Add #1 and #2, and you get a statistic that is almost 100% luck. How can this be? Surely there are players or lines who are higher-percentage finishers than others and can also play adequate defense? I'm not saying there aren't but for the vast majority of NHL regulars, a high PDO in one season comes crashing down the next. And many players with high one-ice shooting percentages get them by cheating offensively, which leaves them susceptible to higher-percentage opportunities against them at the other end of the ice.
If I could pick one statistic I absolutely wouldn't want to bet against, it would be this one.