There is no longer any debate about the value of statistical analysis in baseball. Every team, regardless of whether the franchise is on the hyper-analytical end of the spectrum or the more traditional end, has a highly valued analytics department that fuels roster and strategy decisions over the course of the season. Analytics has become so advanced within baseball that there are even different schools of thought that are emerging within the field.
One of those deviations is within how to construct and manage a pitching staff, and this divergence is on display in the National League Championship Series matchup between the Los Angeles Dodgers and Milwaukee Brewers. All analytics is focused on how to create the largest share of wins from a limited pool, but the best path to those wins is open to question.
When evaluating pitching staffs, traditional analytics values the number of quality innings that a pitcher can provide and the number of high-leverage innings a pitcher throws. The first analytical statistic a team will often consider is WAR, which stands for Wins Above Replacement. In simple terms, WAR measures how many wins a player will earn his team over the typical player called up from Triple-A, snatched off the waiver wire, or signed as a free agent midseason.
In 2018, the National League leaders in Pitching WAR, according to Baseball Reference, were Aaron Nola (10.5 WAR), Jacob DeGrom (9.6), Max Scherzer (8.8), Kyle Freeland (8.4), Jameson Taillon (4.7), and German Marquez (4.7). Every single one of them is a starting pitcher. There are no relievers in the Top 10. In fact, there are no relievers in the Top 40. According to Baseball Prospectus, which favors a different statistic that essentially measures the same thing in Pitcher WARP (Wins Above Replacement Player), the most valuable relief pitcher in terms of wins earned for his team throughout major league baseball is Milwaukee's Josh Hader at #45.
However, when one studies the inning-by-inning production of a pitcher, an argument for the value of bullpen arms emerges. On average, an inning pitched by a relief pitcher is often far more effective than one pitched by a starting pitcher. When one sorts the Baseball Prospectus leaderboard by DRA (an adjusted measure of the traditional ERA stat, which attempts to eliminate ballpark and team defensive quality biases), a new pattern develops. Of the top 45 pitchers in DRA, only nine of them are starting pitchers. Only Scherzer and DeGrom from the previous list are among them. Closer Edwin Diaz of the Seattle Mariners leads the major leagues in this category for 2018.
This makes sense in a practical light. A starting pitcher has to play a long game because they are going to face hitters three or four times each night. Major league hitters are excellent at making adjustments, so a starting pitcher has to consider how to set up a hitter through all four plate appearances. Furthermore, the starter has to pace himself to throw 100+ pitches a night, rather than throwing with maximum effort. A relief pitcher has no such issue. He can come into the game and throw 98-mph bullets for fifteen pitches and be done with it, typically only facing each batter one time.
The Dodgers, a big-market team with a payroll over $200 million, has a starting rotation of Walker Buehler (3.4 WAR), Clayton Kershaw (3.4), Ross Stripling (2.4), Hyun-Jin Ryu (2.2), Rich Hill (1.5), and Alex Wood (1.3). The Dodgers' starting rotation was worth 14.2 wins above replacement. Milwaukee, on the other hand, a small-market team with a payroll just over $100 million, featured a starting rotation of Jhoulys Chacin (2.0 WAR), Wade Miley (1.5), Chase Anderson (1.2), Freddy Peralta (0.4), Junior Guerra (0.0), Zach Davies (-0.2), and Brent Suter (-0.3). Their rotation was only worth 4.6 wins above replacement. So essentially, the Los Angeles starting rotation was worth nearly ten more wins in 2018 than Milwaukee's.
So how did Milwaukee win 96 games while the Dodgers only won 92? One might point to a potent Milwaukee offense that scored 754 runs while slamming 218 homers and leading the league in stolen bases with 124. Except-- the Dodgers led the National League with 804 runs while crushing a league-leading 235 homers. So the Dodgers have both a clear edge in batting and starting pitching.
Where Milwaukee has excelled is in the bullpen. Another advanced metric, known as Pythagorean Won-Loss Record, is a measure of expected wins for a team based on how many runs they score and surrender. The pythagorean win expectation for Los Angeles based on their statistical performance was 102 wins, while the expectation for Milwaukee was 91 wins. One way that Milwaukee has been able to increase their expected win totals was due to the performance of their bullpen in high-leverage situations.
A run surrendered in the first inning of a tie game is not nearly as damaging as a run surrendered in the ninth inning. The deeper into a game that the score remains close, the higher leverage a run becomes. A look at Milwaukee's DRA statistics reveals a bullpen of Josh Hader (2.00), Corey Knebel (2.53), Jeremy Jeffress (2.62), Brandon Woodruff (3.16), and Jacob Barnes (3.54). They have been great in high-leverage situations.
It cannot be denied that everyone would love to have pitchers like Clayton Kershaw ($35 million annual salary), Rich Hill ($16 million), Hyun-Jin Ryu ($7.8 million), and Alex Wood ($6 million), not to mention lights-out Dodgers closer Kenley Jansen ($11 million), the fact is that a team like Milwaukee cannot afford them. Kershaw alone costs more than a third of Milwaukee's total payroll. Here is where the divergence in analytical thinking comes into play.
Those five key members of Milwaukee's bullpen cost the Brewers $7.2 million, or less than the individual salary of three of the Dodgers' starting pitchers or their closer. Good starting pitchers are valuable, and as such, they cost a lot of money. Good bullpen arms can be had much cheaper, so teams like Milwaukee and Tampa Bay are turning more and more innings over to the guys who will get three outs at a time than the workhorse starters they can't afford.
Whether this strategy becomes a small-market versus big-market ploy or is the wave of the future in major league baseball remains to be seen. In the meantime, the collision of these two analytical philosophies is being played out by Los Angeles and Milwaukee in the NLCS.