In this, the age of Baseball Enlightenment, few things are as divisive as the role of relievers. Many believe relief pitching is nearly fungible, that just about any big league quality pitcher can step in and be an effective reliever.
Others, usually with stinging losses still at the front of their minds, firmly believe the difference between winning and losing lands squarely on the shoulders of relief pitchers with enough regularity that the job is best left to proven professionals. If any Joe could step in and be a good reliever, any old Joe would do just that.
The obvious truth is a good bullpen is integral to being a good team. Many bad teams have great bullpens, but few good teams have bad bullpens. Does building a super bullpen full of high octane arms give teams a legitimate leg up?
Just as it is obvious that a good bullpen is key to a good team, the makeup of a quality bullpen seems obvious, too. A bunch of guys who don’t give up runs sounds good enough to me. When looking back and trying to “evaluate” such claims, it gets dicey. Do we use the standard go-to stat Wins Above Replacement? It certainly helps lay the “how much does a good pen add?” question bare. But WAR and bullpens don’t often mesh, not as well as we’d like.
Win Probability Added is another strong measure of a collective bullpen’s worth. WPA is good because it asks not “how?” but “how many?” WPA cuts all the mumbo-jumbo out of the equation and just focuses on the game situation. Did you get the outs? Cool. That’s it.
Via Fangraphs, here are the top 20 bullpens (by WPA) since the strike with the WAR and team record & outcome for fun.
|2002||Braves||11.22||6.6||101 (Lost, NLDS)|
|1995||Indians||10.73||6.7||100* (Lost, WS)|
|2001||Yankees||10.47||8||95 (Lost, WS)|
|2006||Twins||10.36||9.7||96 (Lost, ALDS)|
|2001||Mariners||10.23||5.9||116 (Lost, ALCS)|
|1997||Orioles||10.22||5||98 (Lost, ALCS)|
|2002||Twins||10.1||6.8||94 (Lost, ALCS)|
|2009||Yankees||9.6||5.2||103 (Won WS)|
|2008||Rays||9.3||3.2||97 (Lost, WS)|
|2006||Mets||9.26||6.7||97 (Lost, NLCS)|
|2011||Yankees||9.11||7||97 (Lost, ALDS)|
|2001||Astros||9.02||5.2||93 (Lost, NLDS)|
|2007||Red Sox||8.73||5.9||96 (Won WS)|
|2011||Red Sox||8.59||7.7||90 (LOL)|
|1999||Braves||8.58||5.3||103 (Lost, WS)|
|1999||Rangers||8.58||7.7||95 (Lost, ALDS)|
Again, this is helpful but not but particularly instructive for many reasons. Number one being the fluid nature of bullpens. Take the 2011 St. Louis Cardinals, for example. Like many teams before them, the defending champs bolstered their ‘pen at the trade deadline. They also received a solid boost from injured hurlers returning to health late in the season.
WAR suggests a good pen can be as impactful as a superstar player. Only three bullpens (of the more than 500 team bullpen seasons since 1995) rated above 9 fWAR, or the value of Matt Kemp/Jacoby Ellsbury in 2011. The average relief corps posts a shade under 3 Wins Above Replacement.
Which results in more regular season wins? For fun, I ran a regression (I shoved some numbers into Excel which, as Ben Lindbergh notes, doesn’t sound as smarty pants as running a regression) and here are the results. Which collective number correlates strongest with team wins?
Win Probability Added comes out with the strongest correlation to team wins, nearly doubling Wins Above Replacement’s R-squared (.41 to versus .22, if that means anything to you.) For argument’s sake, both ERA and FIP relate negatively with total team wins. WPA is, of course, not without its shortcomings. As with any assessment of pitching we must account for defensive input and considerable contributions of a capable starting staff.
Using my considerable excel skills, I know now 34 teams won more games than they lost after their bullpen posted a collective negative WPA. The 1999 Diamondbacks won 100 games with a negative WPA from their ‘pen. The 2000 Snakes won 85. The 2001 team won the World Series. How did they manage that? I’m not 100% sure but I think the 40 fWAR over those three seasons from Randy Johnson and Curt Schilling helped.
Two playoff teams from 2011 posted negative WPA from their bullpens: for two very different reasons. The Cardinals posted -2.09 (and just 1.2 WAR) but, as already mentioned, what that bullpen was at the end of the season differed wildly from the group that posted brutal numbers for much of the year.
The 2011 Tampa Bay Rays similarly snuck into the playoffs with a below-average pen. The Rays not only notched a -0.32 WPA but a meagre 0.7 WAR. One good reason for that low number? They pitched an incredibly small number of innings. Less than 400 in total, the fewest innings pitched by a club since 2002 and the 11th lowest number in this entire sample. Good starting pitching is clearly your best reliever.
Having a great bullpen is a nice luxury for teams. It isn’t exactly the first place you start building if winning titles is your endgame. Like the Cardinals in 2011, you can always add effective pieces as the season wears on to fit the particular needs of your club. Or, like the Blue Jays, you load your bullpen with high quality pieces with another endgame in mind: eagerly extracting value from those glory-hunting clubs with championship aspirations.
Like many teams successfully demonstrate on a yearly basis, if you excel in one area of the game you are free to “borrow” from other, weaker areas of your team. Please to enjoy this Google Doc of all World Series winners since the strike on one sheet and the full dataset on another if you’re interested. You can’t win a title without a bullpen but you can’t ride one exclusively to glory.