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The importance of fixing the bullpen

A look at the damage done to the White Sox' 2014 win total by the relief corps

One of the reasons the White Sox bullpen has gone belly-up
One of the reasons the White Sox bullpen has gone belly-up
Kelley L Cox-USA TODAY Sports

From Gordon Beckham to the back three slots of the rotation, there's been plenty of reasons to explain the White Sox' sub-par record in 2014, but it's the bullpen that's served as the team's most prominent punchline.

A month or two ago, it was frequently said that the White Sox could be in contention if they had an average bullpen.  This sort of statement wasn't exactly spot-on, but given the meltdowns we've witnessed from relief pitchers that have been stretched to roles beyond their talent level, it hardly seemed like these comments were coming from the corner of hope and crazy, either.

Now that we've moved closer to the end of the season, things have changed a bit, but the fact remains that the bullpen has cost the White Sox some wins and White Sox fans some hair from their heads.  To get a sense of how critical a bullpen rebound is for 2015, it would be useful to estimate the number of wins that White Sox relievers have let slip away relative to an average team.  To get a sense of the increase in the demand for Rogaine on the South Side, it wou-....nevermind, let's stick to the baseball stuff.

The current gold standard for estimating a player's net value to his team has been Wins Above Replacement (WAR). WAR is very useful if you don't care about the timing of events within games, but since we're talking about the bullpen and events that have already happened, context is very important.  Relief pitchers are on the mound for many of the highest-leverage situations that come up over the course of the season.  Though they throw fewer innings than starters, it's more likely that a given individual pitch from a reliever will wind up deciding a game.

To wit, WAR makes the Sox bullpen look like a problem, but not a huge one.  White Sox relievers have collectively been worth 0.1 wins by FanGraphs WAR in 2014.  League average is currently close to 2.3 wins.  Replacement level is bad, and two-ish wins isn't nothing, but we've all been watching this season.  Surely the bullpen has been more of a problem than this?

Well, to get a more context-sensitive view of the way things have unfolded, we can look at a statistic called Win Probability Added (WPA).  WPA is one of the easier sabermetric statistics to understand.  At every point in the game, you can estimate the odds that your team will win.  The outcome of every plate appearance changes those odds, and that change is accumulated in the pitcher's WPA.

For example, in the eighth inning of Monday's game, the White Sox were down 3-2 and the Orioles had the bases loaded with two outs.  The White Sox had a 22.3 percent chance of winning the game at that juncture.  Then, Matt Lindstrom gave up a bases-clearing double to Jonathan Schoop.  That reduced the White Sox' chances of winning to 3.1 percent.  Matt Lindstrom's WPA was therefore credited on that play with the difference of -0.192 (-19.2 percent).

In that sense, I like to think of WPA as a mirror for a fan's feelings while watching the game.  Huge, clutch plays that help the winning effort the most get the loudest of cheers and high WPA scores.  The biggest choke jobs that turn a potential win into an almost-certain loss get painful groans and large, negative WPA scores.

As one might expect, the White Sox' bullpen's aggregate WPA is large and negative for the 2014 season.  It sits at -4.35, second-worst in baseball behind the how-is-this-even-possible -6.48 of the Rockies.  Because relief pitchers generally only face opposing hitters only once and managers can choose to use them in advantageous situations, relievers generally have a positive WPA in the aggregate.  The average major league bullpen has a 2.09 WPA thus far in 2014, close to six and a half games higher than that of the White Sox' bullpen.

Six or seven games seems like a much more accurate representation of the damage done by the 2014 bullpen than the two or so games suggested by WAR.  By this measure, an average bullpen would still have the 2014 White Sox on the outside looking in from a playoff perspective, but they'd stand a pretty good chance of being above .500.

This all sounds pretty pessimistic, but looking ahead to next season, the message could also be that a turnaround isn't that far away.  Due to the relatively low cost of relievers and their general year-to-year volatility, the bullpen is the easiest unit on a major league team to fix quickly.  Even though the Sox are multiple arms away from a relief corps that looks average, it's certainly feasible for Rick Hahn to acquire the necessary pieces to meet that standard.

So if next year's bullpen is average at its core, does that automatically make the 2015 White Sox six or seven wins better?  Not quite.  Getting some good relievers is half the battle.  Some things, like random BABIP fluctuations and the timing of events within games factor heavily into a bullpen's WPA, and these things are out of everyone's control.  What could be said, however, is that a combination of better relievers and average luck could get the White Sox close to a improvement of that magnitude.  Toss in the likely upgrades to the rotation and lineup, and suddenly, you've got a team that needs to be taken seriously.