On-Base Perception

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Why are strikeout rates at an all-time high?

Chris Carter of the Houston Astros walks to

Chris Carter of the Houston Astros walks to the dugout after a strike out against the Seattle Mariners at Minute Maid Park. (April 22, 2013) (Credit: Getty Images)

When Mariano Rivera struck out Jason Castro to close out Tuesday night's Yankees victory, it marked the 267th time an Astro had struck out in 27 games. Going into Saturday's games, they had struck out 300 times in 30 games, or 10 per game, the most in the majors.

Fun fact: Thursday's 18 strikeouts marked the 15th time that the Astros were rung up in double figures.

It's not just the Astros, though. Entering play Thursday, the MLB strikeout per nine innings rate was 7.71 -- the highest ever, surpassing the 2012 record rate of 7.56, which surpassed the 2011 rate of 7.13.

Although the strikeout rate has risen every season since 2008, it hasn't always been that way.

From 1901-49, K/9, the rate of strikeouts per nine innings, fluctuated little. Pitchers had a 4.04 K/9 in 1911 and 3.92 K/9 in 1946. Each were high-water marks for their respective decades.

Then in 1959 the rate jumped to 5.13, the first time K/9 surpassed 5.0. By 1967 it had climbed to 5.99 and in 1968 pitchers dominated hitters so ferociously -- NL Cy Young winner Bob Gibson went 22-9 with a 1.12 ERA and 268 strikeouts in a season in which seven pitchers had at least 10 wins and an ERA in the ones -- that MLB lowered the mound from 15 inches to 10 to give the batters a break.

That helped steady strikeout rates for a time, but eventually pitchers learned to do well a little closer to the ground. The K/9 rate jumped above six in 1987 (6.01), the first time it ever crossed that threshold. Since then it has climbed like a Giancarlo Stanton moon shot.

One of the biggest reasons for the glut of punchouts seems to be the development of the specialized reliever. Starting pitchers didn't break the 6.0 K/9 threshold until 1995, lagging behind relievers, who crossed the line in 1962. Relief pitchers have been striking out more than seven batters per nine innings since 1995; starters reached that plateau only last season.

Another is a growing culture of power hitters -- such as Adam Dunn, Mark Reynolds or Dan Uggla -- content to trade strikeouts for home runs. They utilize low swing rates (leading to low contact rates) in search of that one, perfect pitch they can drive beyond the outfield wall.

But this is about pitching.

The next frontier -- 8 K/9 -- already has been broached: Relievers had an 8.37 K/9 in 2012. Starters -- you're on the clock.

There may be other factors, though. Pitchers have added more than a mile per hour to their fastballs since those stats began being kept in 2002 and increasingly have ditched their fastballs for cutters during that span.

So are more strikeouts simply good for pitchers and bad for hitters? Well, studies have shown it's neither. It's just . . . different.

If a batter strikes out he obviously can't make a "productive out," advancing a runner via groundout or flyout. But he also can't hit into a double play. Baseball Prospectus research has shown these events essentially cancel each other out.

Though that's likely little consolation to the Astros.

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