Baseball Musings
Baseball Musings
January 02, 2006
On the Ground and In the Air

Update 1/3/2006: Read through for a correction.

Cardinals Diaspora posts on the ground ball/fly ball ratios of the St. Louis starters and relievers. He finds the Cardinals like to hire pitchers who induce ground balls.

For a long time I've been bothered by ground ball/fly ball ratios, and since nothing is happening in major league baseball today, I thought I'd do a bit of research.

I don't believe there is a consistent view on what to measure when you're comparing ground balls and fly balls. STATS, Inc. would publish the ratio of all fly balls to all ground balls, leaving out line drives. Elias used to publish ground outs vs. fly outs, but I don't know if they included line outs in the fly outs. While the Ground/Fly ratio for the majors is around 1.2, the ratio of those on outs is close to 1. Here's a chart showing the percentage of each type of ball given up between 2002 and 2004 (bunts are not included, since a pitcher can't induce a bunt):

G = Ground Ball, F = Fly Ball, A = Air (Fly + Liners)
All Ground Fly  Line G/F G/A
2002 0.433036 0.354243 0.212721 1.222426 0.763781
2003 0.432865 0.342379 0.224756 1.264288 0.763249
2004 0.442254 0.370376 0.187371 1.194068 0.79293
Outs Ground Fly Line G/F G/A
2002 0.460225 0.457944 0.081831 1.004982 0.852624
2003 0.466018 0.446196 0.087786 1.044424 0.872721
2004 0.463908 0.454623 0.08147 1.020424 0.865351

So it really matters if you include line drives. Pitchers in general get more balls in the air than on the ground. Notice two, that a fly ball is more likely to be turned into an out than a ground ball. About 35% of balls in play are fly balls, but about 45% of a pitcher's outs come on those same cans of corn.

So do ground ball/fly ball ratios really tell us anything? The data set is from 2002 to 2004, so I looked at all pitchers in that time frame with 400 innings pitched, and correlated their ERAs with the various ratios:

Pitchers with at least 400 IP, 2002-2004
RatioCorrelation with ERA
G/F-0.137
GO/FO-0.125
G/A-0.155
G/AO-0.114

There are three things you can glean from this chart:

  • Ground/Fly ratios have very little to do with ERA.
  • If anything, the correlation favors who give up a higher ratio of ground balls to fly balls, no matter how you measure them.
  • The overall G/F ratio is a better measure than the number of outs on those balls.

I can certainly imagine that certain parks and certain defenses can change this calculation. But in general, we shouldn't worry about how balls are put into play against pitchers.

The data used in the correlation study is included in the extended entry.

Correction: I fixed point 2 above from lower to higher. Thanks to the people in the comments who pointed this out.

PitcherERAG per FGO per FOG per AGO per AO
Randy Johnson2.791.281.060.790.87
Pedro Martinez2.841.040.910.680.78
Johan Santana2.840.760.620.530.54
Jason Schmidt2.990.960.780.640.68
Tim Hudson3.042.412.031.351.58
Carlos Zambrano3.081.961.651.141.34
Mark Prior3.080.940.720.610.62
Curt Schilling3.171.100.900.700.74
Roy Oswalt3.191.381.170.820.97
Brandon Webb3.243.653.621.782.52
Kevin Brown3.322.101.841.181.46
Roy Halladay3.332.602.321.441.86
Barry Zito3.490.840.670.590.59
Kerry Wood3.501.030.860.670.75
Jacob Peavy3.531.100.880.710.74
Odalis Perez3.551.671.481.011.23
Greg Maddux3.561.981.881.111.46
Al Leiter3.561.070.830.700.70
Josh Beckett3.611.180.930.780.82
Tomokazu Ohka3.631.331.100.800.92
Tom Glavine3.641.371.130.850.91
Wade Miller3.661.201.030.760.89
Vicente Padilla3.681.521.370.941.10
Livan Hernandez3.711.401.170.840.96
Roger Clemens3.711.351.180.840.99
Woody Williams3.710.970.780.630.67
Mark Mulder3.721.951.701.161.39
Kip Wells3.721.731.541.031.30
Steve Trachsel3.731.120.940.720.80
Ben Sheets3.741.281.070.810.91
Andy Pettitte3.761.811.431.001.12
Matt Clement3.801.721.541.031.24
Joel Pineiro3.821.291.070.830.92
Doug Davis3.831.241.000.780.83
Randy Wolf3.850.960.800.630.67
Russ Ortiz3.851.181.010.740.85
Oliver Perez3.860.770.580.540.50
Mark Buehrle3.871.431.220.861.01
David Wells3.881.281.120.800.90
Jamie Moyer3.890.890.750.610.65
Bartolo Colon3.901.030.840.690.71
Kevin Millwood3.931.190.950.710.77
Mike Mussina3.961.130.970.720.82
Jake Westbrook3.972.902.721.502.00
Matt Morris3.971.561.410.991.20
Javier Vazquez3.970.910.740.610.64
Brad Penny3.981.221.040.790.87
Tim Wakefield3.981.050.920.730.82
Carl Pavano3.991.341.140.800.92
Brian Lawrence4.001.841.621.091.34
Jarrod Washburn4.010.740.570.510.50
Carsten Sabathia4.031.120.930.710.77
Carlos Silva4.041.791.541.081.30
Hideo Nomo4.050.890.770.570.64
Derek Lowe4.073.553.271.862.53
Ted Lilly4.090.780.670.520.58
Kirk Rueter4.111.501.290.891.02
Kelvim Escobar4.131.241.050.820.94
Brad Radke4.141.090.930.690.77
Elmer Dessens4.141.551.320.961.10
Ryan Franklin4.170.790.610.540.53
Mark Redman4.170.990.780.660.67
Miguel Batista4.211.821.521.081.30
Rodrigo Lopez4.221.170.980.750.83
Freddy Garcia4.241.100.940.720.82
Kazuhisa Ishii4.300.780.610.540.54
Jason Marquis4.341.761.551.031.25
Jeff Weaver4.381.140.940.700.81
Kenny Rogers4.391.451.300.821.01
Sidney Ponson4.401.631.451.011.22
Ramon Ortiz4.420.960.840.630.71
JohnT homson4.431.221.030.740.87
Adam Eaton4.441.010.890.670.77
John Lackey4.441.130.980.690.81
Esteban Loaiza4.571.241.050.770.88
Jeff Suppan4.581.391.210.841.00
Kris Benson4.591.030.880.640.75
Victor Zambrano4.601.271.050.810.89
Brett Tomko4.611.301.130.810.95
Paul Wilson4.621.181.000.730.83
Jason Johnson4.641.391.110.820.91
Jon Garland4.671.241.100.790.93
Brian Anderson4.681.010.890.620.75
Joe Kennedy4.681.100.900.720.79
Eric Milton4.700.610.490.440.44
Josh Fogg4.701.351.190.830.99
Kyle Lohse4.741.020.830.680.73
Mike Hampton4.741.851.471.021.16
Darrell May4.810.720.610.510.54
Glendon Rusch4.811.291.050.780.88
BrettMyers4.841.591.470.951.21
Cory Lidle4.851.661.460.951.15
Mike Maroth4.861.401.160.840.97
Mark Hendrickson4.881.301.110.790.90
Ismael Valdez5.000.980.850.630.74
Jason Jennings5.061.551.350.891.10
Aaron Sele5.201.080.870.680.74
Ryan Drese5.341.761.480.961.17
Tanyon Sturtze5.410.990.770.610.66
Steve Sparks5.511.251.090.800.95
Shawn Estes5.571.691.601.001.33

Posted by David Pinto at 04:35 PM | Pitchers | TrackBack (0)
Comments

Correct me if I'm wrong David, but doesn't a larger negative number for correlation mean that there's a smaller correlation? Or is it the absolute value of the number that matters?

Posted by: Adam B. at January 2, 2006 05:51 PM

But a decent pitcher can induce a fly or ground ball on a bunt. When a guy sets up to bunt (and most do so before the last second), a pitcher knows that a high pitch will likely induce a pop up whereas a sinking pitch will induce a ground ball. So unless I'm playing too many innings on my PS2, I'm thinking bunts should be included.

But I have to say I love the research you just did and compiled!

Posted by: Devon at January 2, 2006 07:15 PM

"If anything, the correlation favors who give up a lower ratio of ground balls to fly balls, no matter how you measure them."

I'm confused. Isn't negative correlation with ERA a good thing?

Posted by: Rob at January 2, 2006 07:47 PM

I agree with Adam and Rob, I would think a negative number would be a good thing in terms of ERA. Either way though, it is a small correlation as the numbers are close to zero.

What are we missing David?

I also agree with Devon, thanks for putting this together.

Posted by: Tom G at January 2, 2006 09:45 PM

I checked MLB stats GO/AO for late inning relievers, & with a few exceptions, those who gave up more air outs
gave up a higher % of home runs. GO/AO may not matter as much for starters, but they seem to matter
for late inning relievers. A fly ball in a late inning, even
if caught, can ruin an otherwise nice day.

Posted by: susan mullen at January 2, 2006 10:05 PM

a negative correlation is DEFINATELY a good thing, and it makes sense: a pitcher who makes batters put the ball on the ground more often SHOULD (can't say anything's a given in baseball) be more successful than a pitcher who gives up flies. and even though ERA is reliant on team defense, and some luck, it is generally a good measure of how successful a pitcher is -- At least, you can't have a good ERA if you totally suck.

why would anyone prefer a pitcher who gave up mostly flies to one who gave up mostly grounders?

Posted by: benjah at January 3, 2006 07:27 AM

If a team had a really crap bunch of infielders, and a fine set of outfielders, they may prefer the FB type pitcher. But how common is that?

This is great analysis, David...which of course, begs more questions. Line drives are clearly the primary killer of pitchers, with the worst pct in play/pct out ratio by far. Yet, fly balls have the highest pct in play/pct out ratio. Is there any way to examine individual pitchers over time, and see how effectively they can control their FB/LB ratio? It seems that pitchers are often consistent in their GB/AB ratio from season to season, which appears to take the luck factor out of the equation. But if pitchers can consistently control their FB/LB ratio, that would actually seem to be the best predictor of ERA. Perhaps GFB/LB would be the ideal pitcher measure?

Posted by: Dave S. at January 3, 2006 08:59 AM
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