2012: Year of Reliever Whiffs

With due respect to landing a quad, it is believed that one of the hardest things to do in organized professional sports is hit a baseball. Relief pitchers across Major League Baseball are taking that to a new level in 2012.

Since 1961, there have been exactly twelve instances of players registering a strikeout rate above 40%. Five of them are from 2012. While the season is clearly not over yet and we could see declines in strikeout rates, this could be considered the greatest group of relievers, relative to strikeouts, in MLB history.

Looking at the top-ten strikeout rates leaderboard for the last five seasons looks like this:


Season Name K%
2012 Aroldis Chapman 47.00%
2012 Craig Kimbrel 45.90%
2011 Kenley Jansen 44.00%
2012 Kenley Jansen 41.70%
2010 Carlos Marmol 41.60%
2011 Craig Kimbrel 41.50%
2012 Ernesto Frieri 40.70%
2012 Jason Grilli 40.30%
2010 Billy Wagner 38.80%
2009 Jonathan Broxton 38.00%

You can see how prominently 2012 is featured here. It’s also interesting that there is but one representative from 2009 and not a single player from 2008. Considering how good Billy Wagner and Jonathan Broxton were in their 2010 and 2009 seasons, it’s also pretty amazing to see how much separation there is between them and Aroldis Chapman, Craig Kimbrel, and Kenley Jansen thus far.

Not that 40% is particularly magical as a strikeout rate, but to accomplish such a level of dominance is pretty rare among pitchers. For relief pitchers, it has been achieved only ten pitchers if we count the first half of 2012. The first time there were two relievers over 40% in a single season was 1999 with Armando Benitez and Billy Wagner. But looking at the top five strikeout rates since 2008 paints an interesting picture:


Season Name K%
2008 Grant Balfour 36.60%
2008 Juan Cruz 33.00%
2008 Carlos Marmol 32.80%
2008 Brian Fuentes 32.00%
2008 Octavio Dotel 31.90%


Season Name K%
2009 Jonathan Broxton 38.00%
2009 Phil Hughes 33.70%
2009 Michael Wuertz 33.60%
2009 Rafael Soriano 33.20%
2009 Joe Nathan 32.80%


Season Name K%
2010 Carlos Marmol 41.60%
2010 Billy Wagner 38.80%
2010 Rafael Betancourt 35.90%
2010 Joaquin Benoit 34.60%
2010 Joel Hanrahan 34.00%


Season Name K%
2011 Kenley Jansen 44.00%
2011 Craig Kimbrel 41.50%
2011 David Robertson 36.80%
2011 Sergio Santos 35.40%
2011 Koji Uehara 35.00%


Season Name K%
2012 Aroldis Chapman 47.00%
2012 Craig Kimbrel 45.90%
2012 Kenley Jansen 41.70%
2012 Ernesto Frieri 40.70%
2012 Jason Grilli 40.30%

No single season in baseball history has ever featured as many strikeout rates over 40% as 2012. This list could lose two players and still hold true. And if we average out all qualified relievers over the last five seasons, the trend is pretty clear:

Each of the last five seasons has seen about a half percentage point jump in average strikeout rate, with the increase between 2011 and 2012 being the greatest at about 1.5%. But if you look at the top five strikeout rates per year over the last five seasons, the gap widens:

After a fairly steady increase between 2008 and 2011, the jump in 2012 is over 4% among the top strikeout relievers.

We’re just a little over half way to the finish line, so we can’t definitively say 2012 features the most dominant group of relievers ever, but the signs are certainly pointing in that direction. The reasons for such a trend are likely multi-layered, with advances in hitter scouting, better utilization of players suited for short relief appearances, a larger talent pool, luck, among many others. But amidst some of the more obvious (and compelling?) league storylines over the course of the remainder of the season, this is one that will be interesting to see play out.

Note: A special shout-out to Bill McAfee who has the lowest strikeout rate for any reliever on record with a 3.8% rate in 1934.




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Michael was born in Massachusetts and grew up in the Seattle area but had nothing to do with the Heathcliff Slocumb trade although Boston fans are welcome to thank him. You can find him on twitter at @michaelcbarr.


16 Responses to “2012: Year of Reliever Whiffs”

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  1. Justin says:

    35 Year old Jason Grilli

    Wow

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    • walt526 says:

      Former Giant pitching prospects traded away long-ago and seemingly forgotten are putting together a collection of nice comebacks. Obviously, Ryan Vogelsong (drafted in 1998 and traded in 2001 for Jason Schmidt) is at the top of the list. But Jason Grilli (drafted in 1997 and traded in 1999 for Livan Hernandez) is having a fantastic 2012 so far and Jerome Williams (drafted in 1999 and traded in 2005 for LaTroy Hawkins) has been a decent back-of-the-rotation guy for the past year-and-a-half.

      He hasn’t exactly been out-of-the-limelight like the others, but Francisco Liriano (amateur FA in 2000 and traded in 2003 for AJ Pierzysnki) has a chance to be another Phoenix from San Francisco.

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  2. Frank says:

    Is it not also strange how much turnover there is in the top 5? Or is 5 such a small number that high turnover would be expected?

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  3. L.UZR says:

    Another crackpot global warming theory supported by data.

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    • Radivel says:

      Relief pitcher strikeout rates related to global warming? We can’t have this.. someone call Al Gore!

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    • bada bing says:

      Yeah, man! I’ve been trying to tell everyone that ‘global cooling’ is occurring, but no one seems to listen to me. I mean, just look at the weather outside today. I would have a much easier job convincing everyone if all these people weren’t so stupid…

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  4. Well-Beered Englishman says:

    This reminds me strongly of the piece from last week about the context for high strike rates. It was specifically adjusting Stephen Strasburg’s unprecedented K rate (for starters) to account for the more strikeout-heavy environment we have nowadays.

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  5. Tim_the_Beaver says:

    How does this compare to K rates for starting pitchers? I’m curious because I wonder how you would tease out a change in pitching talent vs. a change in hitting talent. That is, are today’s hitters more strikeout happy? (didn’t I see a post about this recently?)

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    • Fletch says:

      I believe there have been articles posted here on FG in the past year or two that essentially show that today’s hitters walk more, strike out more, and hit more home runs than hitters in previous eras. Basically, the three true outcomes are much more prevalent in today’s game than ever before. Feel free to correct me if I have this wrong, and I’ll try to dig up the links.

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  6. nosuchthingasacoincidence says:

    Let’s talk about how they’re all national leaguers.

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    • phoenix2042 says:

      2008-2011 was 12-8 AL-NL (unless I’m mistaking a couple), and only 2012 is all NL. Maybe it’s just a fluke this year because I assume that relievers don’t face many pitchers in the NL (at least not as the same right as starters)

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  7. John C says:

    Wouldn’t a half season worth of data usually present a greater number of outliers than a full season, or am I missing something?

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  8. Undocorkscrew says:

    A bit OT, but looking at Craig Kimbrel’s numbers since May 14th is making me all giddy…..

    19 Appearances, 3 hits, 1 run, 0 BB, 32 K

    Can’t believe his BB rate now, it’s a lovely thing to see.

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