The corollary of that, though, is that it's also the era of strikeouts. Players K more than they have before, and unlike the home run binge, strikeout rates continue to go up.
American League hitters fanned a record 14,925 times in 2008, an increase of 35 from a 2007 total that had been a record. The National League also set a new mark in 2008, with 17,959 punch-outs. AL teams have averaged 1,000 strikeouts per club 10 times in history, while NL clubs have hit that mark 13 times. All of those occurrences have been in the past 13 years.
And as the preponderance of strikeouts has increased, the perception of them has changed. Whereas once a player was considered less than a complete hitter if he struck out too often, new ways of looking at the game have mollified that perception.
A player who strikes out 100 or more times can still be thought of as a winning player if he does the other things right: specifically, getting on base and hitting for power. For a hitter, the key question is: Did you make an out, or not? Above anything else, "statheads" rightly boil things down to that fundamental issue. Outs are bad. Any plate appearance that does not end in an out is good.
One of the poster boys for this thought process is free agent Adam Dunn. The slugging outfielder has struck out more than 160 times in each of the past five seasons. But he's also hit at least 40 homers, drawn more than 100 walks and posted at least a .365 on-base percentage in each of those campaigns.
Dunn certainly has his critics, but his value is much more appreciated now than it would have been, say, 30 years ago. It's thanks in part to context, since his strikeout totals don't seem so exaggerated in a league in which 100 or more K's in a season just isn't that unusual. But it's also thanks to the quantitative analysis that has emerged in baseball writing and thinking over the past two decades.
Yet those same analysts who urge readers to ignore a hitter's strikeout totals also advocate paying great attention to pitchers' strikeout numbers. At first blush, it's a contradiction. Upon further review, it makes a lot of sense.
One of the great advances in analysis in recent years was the concept of defense-independent pitching statistics, as initially introduced by Voros McCracken. His controversial notion was that a pitcher has very little influence on what happens to a ball once it's in play.
A pitcher, to a large extent, controls strikeouts, walks and home runs. Each of those outcomes -- sometimes half-jokingly called the "three true outcomes" -- is a pure measure of the battle between hitter and pitcher. But on a ball in play, the outcome lies much more in the hands of the defense.
What that means is that strikeouts, walks and homers tend to be predictable from season to season for a pitcher. They're not susceptible to fluctuations in the quality of his defense. Instead, they more closely reflect the pitcher's own ability. It's somewhat like the difference between homers and RBIs for a hitter. One, you do on your own. The other, you need help from your teammates.
That, in turn, sheds light on why strikeouts are so valuable in assessing a pitcher. It's not necessarily that they tell you everything in an evaluation. They don't paint a full picture of what a pitcher was this past year. But because a pitcher's strikeout rate tends to be consistent, it's also predictive.
And prediction is the key. Assessing the value of what's already been done isn't really that hard. Making educated guesses about what's to come is the tough part. A pitcher who has the ability to put hitters away without relying on his defense is a pitcher who's likely to keep succeeding. Likewise, a hitter who hits the ball out of the park and gets on base, but strikes out a lot, is also likely to keep doing so.
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.