Looking at the 2006 FIP (fielding independent pitching) and DER (defensive efficiency ratio), the A's allowed substantially fewer runs than expected...
I was looking at The Hardball Times' stats page the other day, and noticed that the A's pitchers had a decidedly mediocre FIP in 2006 (FIP stands for Fielding-Independent Pitching, and is like ERA, but based solely on things the pitcher has some control over, like walks, strikeouts, and home runs).
This wasn't a huge surprise-- several A's pitchers, most notably Barry Zito, got much better results than their peripheral stats would suggest. So how did the A's allow so few runs, if their pitching wasn't that good?
At first, I assumed that they turned a lot of balls-in-play into outs, either because their home park makes fielding easier (it does) or because their fielders were good (I thought they were). A quick look at their Defensive Efficiency Ratio (DER-- basically outs per ball-in-play) shows that they were only average at turning balls-in-play into outs.
This is strange. The A's allowed fewer runs than most teams in the league, but both their FIP and DER are only average. Below, you can see ERA, FIP, and DER for all the AL teams (taken from the Hardball Times):
Team ERA FIP Diff DER
TB 4.96 4.86 -0.1 0.673
CLE 4.41 4.39 -0.02 0.677
KC 5.66 5.31 -0.35 0.677
BAL 5.35 5.15 -0.2 0.681
TEX 4.6 4.52 -0.08 0.681
BOS 4.83 4.56 -0.27 0.682
MIN 3.95 4.05 0.1 0.687
League 4.56 4.56 0 0.688
OAK 4.21 4.44 0.23 0.69
SEA 4.6 4.6 0 0.692
LAA 4.04 4.09 0.05 0.693
CHA 4.61 4.55 -0.06 0.696
TOR 4.37 4.51 0.14 0.696
NYA 4.42 4.45 0.03 0.697
DET 3.84 4.36 0.52 0.704
The "Diff" column is the difference between the teams' FIP and ERA. This difference should be mostly determined by the teams' DER (it's not necessarily a simple relationship, but two teams with the same DER should have about the same difference).
You might have noticed a couple teams really stand out. Detroit had a huge difference between their FIP and ERA, but that was driven by an amazing DER. The A's, on the other hand, had the second largest difference (0.23 runs per game, or about 37 runs over the season), but a DER very close to league average. Seattle and Minnesota, the two teams above and below the A's in DER, had differences of 0 and .1, respectively. Boston and Kansas City stand out in the wrong way-- the (negative) difference between their FIP and ERA seem out of line with their DERs.
So what drives this variation? The answer, I believe, is "Situational Pitching." Essentially, the A's got more outs at crucial moments than we would have expected, given their overall play, while Boston and KC got fewer outs than expected.
What does this mean going forward? I don't believe the A's pitchers are truly more "clutch" than their counterparts across the league, which means the A's got lucky-- and Boston was unlucky. The 37 runs the A's prevented through "Situational Pitching" were certainly the difference between making the playoffs and finishing second, but it seems unlikely that they can do it again in 07. On the other hand, Gary Matthews Jr. was signed by the Angels to 5yr/50MM contract, so there's always hope.