This is intriguing, although it might end up not being much at the end of the season. It is very difficult to finish the season with such a low ERA as a reliever because one or two bad outings can wipe out many good outings. I went back and looked at how many pitchers were at this level (20 IP, 2.25 ERA) at the All-Star Break the last few years.
It's similar to the numbers with the explosion of strikeouts in the past few years. After hovering in the 20's and low 30's for a decade, it has moved up dramatically since 2010. There are also 9 pitchers right now with between 15 and 20 innings pitched and an ERA under 2.25. It wouldn't be surprising if the number at the All Star Break this year is in the mid-50's.
Then the question will be how many of them can hold onto it for the rest of the year. If there are 40 or more pitchers at the end of 2013 with at least 40 IP and an ERA under 2.25, that would show how much the game has changed.
The increase in dominant relievers who can strike batters out almost at will without allowing many hits or walks has tipped the balance away from the hitters in a way that might be difficult to reverse any time soon.
25+ IP, 2.5+ K/BB (highest # in a season)
This could help explain why hitters are striking out like there is no tomorrow. It was an all time record when there were 125 pitchers with at least 25 IP and at least a 2.5 K/BB ratio. Four years later, the number of pitchers who did that nearly doubled, and it seems likely to continue. While the long term trends might be easy to spot, it is stunning how rapidly some these numbers are moving.
Average Team Batting Average
Another trend to watch, along with the skyrocketing strikeout rate. My guess is that it holds steady for the rest of the year (average is .251 in both April and May), but it could slide even further as we get into the summer months.
Just as with the explosion of strikeouts, it is unbelievable how quickly the game has shifted in the last few years. There are still teams at the top that can mash (Rangers, Tigers, Indians, etc.), but the number of teams that have anemic offenses just keeps getting worse.
As you can see, the Royals have been remarkably consistent over the 13 years. They have averaged a 26th place in ERA. That is clearly one of the worst, and probably the worst over that time period (the other usual suspects like the Orioles and Rockies have fluctuated enough that they're probably a bit better). The Royals, who are a pleasant surprise at 13-9 aren't hitting much (20th in runs, 12th in OPS) and while they have some good hitters, they're not going to hit their way to the playoffs.
How have they done it? They're 6th in starting ERA and 7th in bulllpen ERA, making for a balanced attack. Last year, they were 6th in bullpen ERA and 26th in starting ERA. The reason this might continue is that their starting rotation is almost completely different from last year.
In 2012, they got starts from Bruce Chen (34 starts), Luke Hochevar (32), Luis Mendoza (25), Jeremy Guthrie (14), Will Smith (16), Jonathan Sanchez (12) and a handful from a few others.
In 2013, they have a starting rotation of Ervin Santana, James Shields, Wade Davis, Jeremy Guthrie and Luis Mendoza. Chen and Hochevar were moved to the bullpen and are pitching very well (1 ER in 15 IP). They acquired Santana in a trade with Angels last October, with Shields and Davis coming from Tampa in a trade last December. No one is mistaking Santana for Justin Verlander, and while he underachieved the last few years, he won 17 games as recently as 2010.
The Royals are lucky to be in a division that will probably have only one other good team (Tigers). The Tigers came out of nowhere in 2006, the Orioles did in last year (although going 16-2 in extra inning games would be hard to replicate), and the Royals have a shot at the playoffs this year if the starters continue to pitch well.
Starters have also improved, but only down to .257 in 2013 from .270 in 2004. This is a startling drop, and is not a surprise considering the huge increase in strikeouts among relievers. Just as with the strikeouts, it is interesting to consider how much further this could go.
It doesn't seem possible that this trend could continue forever, but could relievers be holding the league to a .220 average in a few years or even .200. Something like that might trigger some kind of response to help the hitters like when the mound was lower after the '68 season. It is possible that this is as low as it is going to go, but we'll have to wait and see.
The lowest total from any month in 2012 was 7.36 in April, which made it higher than any individual month from 2005 to 2011. The trend here is remarkable, but it obviously can't continue going up like this forever. It does not seem at all ridiculous to assume that pitchers could average over 8 strikeouts per 9 innings for an entire month and then an entire season.
Why is this happening? This article from Tyler Kepner in the New York Times before the season started discusses several different possibilities, one of which is increased specialization in the bullpen. As more and more great pitching prospects are placed on a path early on in their careers to be a bullpen strikeout specialist, we will see more astonishing seasons. In 2012, there were 4 pitchers (Craig Kimbrel, Aroldis Chapman, Kenley Jansen, Ernesto Frieri) with at least 60 innings and a K/9 average of over 13 (there was a total of 9 between 2000 and 2010).