I find this fascinating. American League teams have scored just 4.53 runs per game in 2010, which is the lowest level that we’ve seen since 1992. This graph shows the ebb and flow of AL offense over two decades:
From 1996-2000, AL teams scored on average about 5.2 runs per game. That number settled down into a fairly consistent 4.7-4.9 per game range for most of the decade, but with a slow trend line down. This season, run scoring has suffered a pretty big 0.3 runs / game drop off.
Your guess is as good as mine as to the cause of the drop off. I think it is some kind of combination of the slow exit of performance enhancing drugs, better use of situational relief pitchers, better practices in raising young pitchers, and some kind of cyclical talent swing. I’d be curious to hear what everyone else thinks.
A tighter run scoring environment means a few things. The value of one run increases versus several runs. That means that things like sacrifice bunts and stolen bases become slightly more worthwhile than they were a few years ago. Your run expediency matrix will change a bit. Starting pitchers will stay in the game slightly longer, meaning that bullpens are less important. You might be able to make a pretty good case that in a 4.50 run world, a 12-man bullpen in the American League is too big.
But most of all, we shouldn’t be as surprised when we see Andy Pettitte and Phil Hughes put up big ERAs. In this environment, a lot more pitchers are going to be impressive, and the impressive ones will be downright dominant.