The chart tells the tale. Prior to the offensive explosion in 1993, the total of starting pitchers who held right-handed batters to an OPS under .600 was usually in the the high teens.
That number fell into single digits in 1993 and, with only a few exceptions, stayed there until 2011.
The current spike thus far in 2014 is likely to subside somewhat as the season plays out, but it remains a striking indicator of what seems to be a changed state of affairs.
