Pitcher Velocity and Run Environments

Last night Will Carroll tweeted wondering about whether the perception was accurate that there were more pitchers thrower with greater velocity than there were in seasons before.  I had been sitting on a couple graphs for a month or so waiting to have something more interesting to say, failing that I published the graphs last night because at least it was timely.  Andrew over at Camden Chat asked about how the change in the number of hard throwing pitchers has affected the run environment.  In this post I compared the number of hard throwing starters (>90 mph) and reliever (>93 mph) to changes in the run environment as measured by starters' or relievers' FIP.  Each point is the data from a single year (2002-2011)

Starters

Click to Enlarge

The R2 for the above graph is 0.86.  That is a tight graph, but it should be stated that correlation does not always mean causation. 

Relievers

The R2 is not as good or the relievers with an R2 of 0.62.  That is still a decent correlation, but again it does not outright say that the increase in velocity is the reason why the run environment has decreased.

Conclusion
The reasons for change in the run environment are likely to be rather numerous.  There has been greater recognition of the value of defense, which decreases run scoring in two ways: better fielding and reduced emphasis on offensive performance.  It is assumed that the reduction in effective PED use has also decreased offensive performances.  Another factor is that, as it always has, that baseball becomes more and more competitive every year.  By that I mean that the players today are better than the players who came before (Yes, the Babe Ruth is Matt Stairs argument).  It may also be that the recent upswing in pitchers who can throw hard has also resulted in dampening the run scoring environment.

Of course, the big question is why are there more harder throwing pitchers?  Here are the various explanations I have determined and collected:

• There are a greater number of highly talented players to choose from.
• Training has vastly improved.
• Preventative and reconstructive medicine has improved.
• Teams may be pushing more athletic, strong-armed players to the mound instead of the field.

On that last point, Keith Law disagreed with me on that one.  As far as I can tell, the four top throwers in the relief corps (Henry Rodriguez, Aroldis Chapman, Jordan Walden, and Daniel Bard) were never given much consideration for playing the field.  It may well be that idea sounds better than it looks when you begin looking at the data.  It may well be that advancements in training and medicine taking effect somewhere between 1995 and 2005 for amateurs may be the primary reason for hard throwing pitchers.  Or it may be that advances made in the 2000s in college and lower minors are improving the development and preserving the health of hard throwing pitchers.