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Biggest differences between FIP- and ERA-

Even though FIP- and ERA- measure different pitching aspects, they often present similar views of a pitcher's season. This post investigates seasons where the two metrics diverge.

By Scott Lindholm
Norm Hall

I saw this tweet a couple nights ago from Neal Kendrick which piqued my interest:

I'm old enough to remember watching Tiant pitch as a kid, but only as a Red Sox--I never saw him pitch in Cleveland, which is just as well. I looked up his 1969 FIP- on FanGraphs and saw it was a horrendous 125. That's a pretty big difference in FIP- vs. ERA+, which got me curious.

The definitions of ERA- and FIP- can be viewed in whatever detail is desired here. I changed Neal's number to ERA- so I could gather all the data from FanGraphs and that the metrics would be on the same scale. To briefly explain, Tiant's 1969 ERA was 1% better and FIP 25% worse than the league, a pretty big difference between the two metrics.

Where does Tiant's season rank? I checked all seasons since 1950 in which a pitcher had 20 or more starts with a ERA- of 99 or lower, meaning his ERA was better than league average. This was over 3,000 player-seasons and I used [ERA-] - [FIP-] to look for the greatest differences.

In Tiant's case this would be (99-125) or -26. This put him in some very select company:

Name Team Year Age G GS W L IP ERA FIP WAR FIP- ERA- Diff
Joe Cowley Yankees 1985 26 30 26 12 6 159.2 3.95 5.54 -0.8 139 98 -41
Pat Mahomes Twins 1994 23 21 21 9 5 120.0 4.73 6.21 0.1 128 97 -31
Joaquin Andujar Athletics 1986 33 28 26 12 7 155.1 3.82 4.93 0.1 126 98 -28
Luis Tiant Indians 1969 28 38 37 9 20 249.2 3.71 4.83 0.3 125 99 -26
Dennis Cook Indians 1992 29 32 25 5 7 158.0 3.82 4.94 0.1 126 97 -29
Steve Stone Orioles 1979 31 32 32 11 7 186.0 3.77 5.06 0.2 127 94 -33
Tom Browning Reds 1988 28 36 36 18 5 250.2 3.41 4.50 0.3 125 96 -29

Click on table to enlarge. Click on column headings to sort.

On the surface there are decent seasons represented, but the relatively low numbers of strikeouts, high numbers of walks, and a tendency toward giving up home runs drove the FIP value higher. These are the pitchers FIP identifies as being the beneficiary of events outside their control.

How about more recent pitchers? This chart shows seasons since 2000 with a difference of -15 or greater:

Name Team Year Age G GS W L IP ERA FIP WAR FIP- ERA- Diff
Chuck James Braves 2007 25 30 30 11 10 161.1 4.24 5.48 0.2 123 96 -27
Jeremy Guthrie Royals 2013 34 33 33 15 12 211.2 4.04 4.79 1.1 119 99 -20
Jose Lima Dodgers 2004 31 36 24 13 5 170.1 4.07 5.09 0.2 120 98 -22
A.J. Griffin Athletics 2013 25 32 32 14 10 200.0 3.83 4.55 1.4 118 99 -19
Jacob Turner Marlins 2013 22 20 20 3 8 118.0 3.74 4.43 0.3 117 99 -18
Paul Abbott Mariners 2001 33 28 27 17 4 163.0 4.25 5.01 0.8 117 99 -18
Dave Bush Brewers 2008 28 31 29 9 10 185.0 4.18 4.93 0.9 116 99 -17
Jason Johnson Orioles 2001 27 32 32 10 12 196.0 4.09 5.12 0.7 120 95 -25

Click on table to enlarge. Click on column headings to sort.

These are seasons we can recall, including three from 2013, A.J. Griffin, Jacob Turner and White Sox nemesis Jeremy Guthrie. This chart has the side benefit of giving a glimpse of the capriciousness of the win as a measure of pitcher effectiveness, but that's an issue for another day.

Often ERA- and FIP- both identify outstanding pitcher seasons--this chart shows pitchers with dominant FIP- and ERA- seasons since 2000:

Name Team Year Age G GS W L IP ERA FIP WAR FIP- ERA-
Pedro Martinez Red Sox 2000 28 29 29 18 6 217.0 1.74 2.17 9.9 46 35
Pedro Martinez Red Sox 2003 31 29 29 14 4 186.2 2.22 2.21 7.8 49 48
Pedro Martinez Red Sox 2002 30 30 30 20 4 199.1 2.26 2.24 7.8 51 50
Randy Johnson Diamondbacks 2001 37 35 34 21 6 249.2 2.49 2.13 10.4 46 55
Zack Greinke Royals 2009 25 33 33 16 8 229.1 2.16 2.33 9.1 53 48
Randy Johnson Diamondbacks 2004 40 35 35 16 14 245.2 2.60 2.30 9.5 48 57
Randy Johnson Diamondbacks 2000 36 35 35 19 7 248.2 2.64 2.53 9.5 52 56
Roger Clemens Astros 2005 42 32 32 13 8 211.1 1.87 2.87 5.6 67 44
Mark Prior Cubs 2003 22 30 30 18 6 211.1 2.43 2.47 7.5 57 57
Randy Johnson Diamondbacks 2002 38 35 35 24 5 260.0 2.32 2.66 8.0 60 54
Josh Johnson Marlins 2010 26 28 28 11 6 183.2 2.3 2.41 6.1 60 56
Rich Harden - - - 2008 26 25 25 10 2 148.0 2.07 2.95 4.5 68 48
Tim Lincecum Giants 2009 25 32 32 15 7 225.1 2.48 2.34 7.5 56 60
Clayton Kershaw Dodgers 2013 25 33 33 16 9 236.0 1.83 2.39 6.5 66 51
Roy Halladay Phillies 2011 34 32 32 19 6 233.2 2.35 2.20 8.1 56 61
Jason Schmidt Giants 2003 30 29 29 17 5 207.2 2.34 2.64 6.6 62 56
Matt Harvey Mets 2013 24 26 26 9 5 178.1 2.27 2.00 6.1 55 63

Click on table to enlarge. Click on column headings to sort.

Look where Matt Harvey was headed before his season ended--that's why I used his picture at the top of this post. These numbers also show just how dominant Clayton Kershaw was in 2013 despite going "only" 16-9. These seasons all have high strikeout rates and few home runs in common, and it's no coincidence the pitchers in this chart are recognized among the best in recent baseball history..

Neal's tweet got my attention because he unearthed one of the few seasons in which FIP- and ERA- went in different directions, and I'm always intrigued by outlier seasons of any kind. And it's always fun to mention Luis Tiant.

...

Thanks to Neal Kendrick of High Heat Stats for the idea and permission to run with it. All data courtesy of FanGraphs.

Scott Lindolm is a web columnist for 670 The Score in Chicago. Follow him on Twitter @ScottLindholm.

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