Luck Factor and the NL bullpen
- Updated: March 25, 2011
We finally get to the last of our luck factor series. For those of you that have been following this all along I give a wholehearted thanks. If you are just joining us you might want to back track and read the first one. It should be archived in the sabermetrics section of this site. There is nothing quite as volatile as charting bullpen performance. However, there are some common elements we notice across the board.
Obviously, defense efficiency ratings should be fairly stable overall. We notice a slight improvement for relief pitchers. There are any number of explanations we could latch onto. Relievers tend to be harder throwers, so more of them are fly ball pitchers. Fly balls tend to become a higher percentage of outs than groundballs. It is more likely though that the change is due to fielders behind the pitchers. Most teams employ defensive replacements in close games. A slow and plodding outfielder is replaced with a fleeter one. This almost universally happens after a starting pitcher has been removed.
Bullpens have higher strikeout rates and higher walk rates. These in combination lend themselves to volatility. On the one hand, bullpens will naturally have higher left on base percentages because of the pitcher’s ability to strikeout more hitters. Then again, the higher walks will lead to more base runners.
There is more volatility among relief pitchers because of the smaller sample size, but we still see some trends. San Diego was the only good pen to suffer from bad luck. Had they had even average luck the Giants wouldn’t have even made the playoffs. That is something to look forward to when the season starts. Meanwhile, the Giants had the best luck out of all of the NL teams.
These numbers are from the 2011 projected bullpens. A quick look over the strikeout and walk ratios will provide one clue in addition to the luck factors. Of course, the FIPs are also a good predictor for future performance. For team predictions, this has to give us pause before picking the Phillies to run away with it all. If we take FIP into consideration then the Phillies won’t even finish in the top half in the NL in ERA for relievers. It’s hard to pick a team to win 110 games or more with a below average pen. The Giants on the other hand are in excellent position to repeat with their rotation and bullpen at the top of the league.