I have thought for quite some time that groundball pitchers were more likely to experience defensive errors behind them for the simple reason that most fielding miscues occur on grounders rather than flyballs. As my high school baseball coach liked to say, "There are no bad hops in the air."

There are three primary reasons why groundballs lead to more errors than flyballs.

1. Groundballs are more difficult to field cleanly than flyballs.
2. Infielders are more likely to make throwing errors on groundballs than outfielders on flyballs.
3. Infielders are also held to a higher standard by scorekeepers than their counterparts.

With respect to point number three, when an infielder throws a ball low, high, or wide of the first baseman, he most likely will be charged with an error if the batter-runner is safe. On the other hand, if an outfielder throws a ball off line while attempting to nail a runner, he won't be charged with an error unless the ball gets away and the errant throw results in the runner advancing an extra base.

If my longheld belief is correct, groundball pitchers should give up more unearned runs than flyball pitchers. I decided to test my hypothesis to see if it is true by analyzing last year's data.

According to ESPN's stats, pitchers allowed 54,981 groundballs and 44,528 flyballs last year. The ratio of groundballs-to-flyballs was 1.23.

By the same token, pitchers allowed 19,760 runs and 18,202 earned runs. The ratio of runs to earned runs was 1.086. Conversely, the ratio of earned runs to runs was .921. In other words, .079 or 7.9% of the runs scored last year were unearned.

Graph courtesy of Dave Studeman, Baseball Graphs and The Hardball Times.

Derek Lowe led the major leagues in unearned runs as a percentage of total runs with .212. That's right, more than one out of every five runs Lowe allowed was unearned. Lowe's high number of unearned runs is partly a function of the number of groundballs he induces. A secondary cause could well be the Dodgers' infield defense, which The Hardball Times Baseball Annual rated as below average in 2005. There is also the potential for scorekeeper bias, as well as a certain amount of randomness, especially when dealing with smaller sample sizes.

Let's take a look at the top and bottom 20 pitchers in terms of allowing unearned runs as a percentage of total runs.

TOP 20 PITCHERS, 2005
UNEARNED RUNS/TOTAL RUNS
162 OR MORE INNINGS

Pitcher          Team         %UER     G/F
Derek Lowe        LAD	   .212    2.92
A.J. Burnett      Fla	   .175    2.42
Jeff Suppan       StL	   .172    1.43
Mark Buehrle      CWS	   .172    1.40
Kevin Millwood    Cle	   .153    1.34
Josh Towers       Tor	   .149    1.23
Roger Clemens     Hou	   .137    1.41
Jason Marquis     StL	   .136    1.59
Scott Kazmir       TB	   .133    1.05
Nate Robertson    Det	   .133    1.59
Carlos Silva      Min	   .133    1.55
Jake Westbrook    Cle	   .132    3.13
Matt Morris       StL	   .129    1.60
Kenny Rogers      Tex	   .128    1.33
Do. Willis        Fla	   .127    1.40
Jamey Wright      Col	   .126    2.06
Br. Claussen      Cin	   .124    0.77
Cory Lidle        Phi	   .114    1.79
Bronson Arroyo    Bos	   .112    0.85
Kip Wells         Pit	   .112    1.29

The top 20 pitchers have a weighted-average G/F ratio of 1.51, or 22.8% higher than the league average (1.23). This would suggest that groundball pitchers are indeed more prone to giving up unearned runs than flyball types.

BOTTOM 20 PITCHERS, 2005
UNEARNED RUNS/TOTAL RUNS
162 OR MORE INNINGS

Pitcher          Team         %UER     G/F 
Joel Pineiro      Sea	   .000    1.29
Brian Lawrence     SD	   .009    1.46
Pedro Martinez    NYM	   .014    0.85
Ryan Franklin     Sea	   .018    0.95
Esteban Loaiza    Was	   .022    1.21
Kyle Lohse        Min	   .024    1.25
Jeff Francis      Col	   .025    1.00
Brad Penny        LAD	   .026    1.32
John Patterson    Was	   .028    0.61
Mark Redman       Pit	   .030    1.64
Aaron Harang      Cin	   .032    0.95
Horacio Ramirez   Atl	   .037    1.60
Johan Santana     Min	   .039    0.91
Freddy Garcia     CWS	   .039    1.60
Jamie Moyer       Sea	   .040    0.87
Brett Tomko        SF	   .040    0.95
David Wells       Bos	   .042    1.51
C.C. Sabathia     Cle	   .043    1.55
Jarrod Washburn   LAA	   .045    0.97
Jon Lieber        Phi	   .047    1.29

The bottom 20 pitchers in terms of allowing unearned runs as a percentage of total runs have a weighted-average G/F ratio of 1.15, or 6.5% below the league average. This data once again confirms that groundball pitchers are more apt to give up unearned runs than flyball types.

I could also present the data by listing the top and bottom 20 in G/F ratio and showing the percentage of unearned runs to total runs. However, for the sake of brevity, I have chosen not to run what amounts to a duplicate effort. Besides, batted ball types have been analyzed more than unearned runs/total runs. Ergo, I thought these lists would generate more new information than the other way around.

Everyone knows that Lowe is an extreme groundball pitcher. But how widely known is it that he also gives up more unearned runs than the average pitcher? Over the duration of Lowe's career, 13.2% of his runs allowed have been unearned vs. a league average of 7.9%.

What can we do with this knowledge? I'll be the first to recognize that I'm not trying to break any new ground here. Voros McCracken, who developed Defense Independent Pitching Stats (DIPS) five years ago; Tom Tippett and Mitchel Lichtman have already beaten me to the punch.

David Gassko wrote an excellent article on Batted Balls and DIPS for The Hardball Times last August in which he concluded that "a pitcher's ground ball rate has a weak, but nonetheless significant, correlation with unearned runs allowed."

Gassko added:

The idea of earned runs, originally, was almost somewhat ingenious; it was the first attempt to separate pitching and fielding. But once we can characterize each outcome independent of defense, the need to separate earned and unearned runs disappears.

I would agree with David and recommend that we pay more attention to total runs than earned runs. Oh, you'll still find me giving an ERA here and there, but recognize that run average (RA) is an even better gauge of a pitcher's performance than earned run average.

Secondly, as it relates to ERA, be aware that a pitcher with a high percentage of unearned runs is more likely to regress than a pitcher with a low percentage of unearned runs. Not surprisingly, pitchers in the top 20 table above have a higher DIPS ERA relative to actual ERA than those in the bottom 20.

Lastly, do not make the mistake of discounting groundball pitchers. All else being equal, a groundballer is preferable to one who gives up flyballs. Yes, groundballs turn into more hits and errors than flyballs, but the latter are more harmful because they result in a greater number of extra base hits and home runs.

[Additional reader comments and retorts at Baseball Primer.]