In recent years we’ve seen MLB teams rely more heavily on elite relief pitching, especially in the postseason. So which is better: an elite bullpen or an elite starting rotation?
For a good portion of the early history of baseball, bullpens were virtually nonexistent. Pitchers would occasionally come in for relief in games they weren’t pitching for a few innings at a time, but there was no such thing as a specialized relief pitcher. It was believed that the best pitchers were starting pitchers. There was no consideration that some pitchers may not succeed as a starter, but could be effective in shorter appearances. The first true MLB relief pitcher was Firpo Marberry in 1920. Although he was the first, relief pitching didn’t really take off until the 1960s. At that point, more relievers were used than ever.
With the introduction of a structured bullpen and pitchers on the roster with the specific purpose of being a relief pitcher came the birth of a starting rotation. In the 1960s, teams often used their best pitchers against the best teams and manipulated their starting pitcher usage to maximize their regular season potential. By the latter part of that decade, a four-man rotation became increasingly popular. In the mid-to-late 70s, teams began to use a five-man rotation. By 1980 almost every team used a five-man rotation.
The combination of both of these factors has caused the CG% (percentage of starts in which pitchers pitch a complete game) to drop dramatically over the past 20 years. In the current game, there seems to be more reliance on relief pitchers than ever before.
Strategic usage of relief pitchers began in the 1990s, but it seems more prevalent than ever before. In 2014 and 2015 we saw the Royals and their superior bullpen nearly complete back-to-back championships. By being extremely successful in the final three innings of games, they were able to create a distinct advantage over their opponents. That advantage became more pronounced during the postseason.
During the Royals’ two runs at a championship, there was much discussion about the advantages of an elite bullpen. This year we saw the discussion of high leverage relievers completely take off. Both Andrew Miller and Zach Britton pitched well enough to be considered for Cy Young votes. Aroldis Chapman helped lead the Cubs to a World Series victory. Top prospects were given up for Miller, Chapman, and Melancon at the deadline. It seems, from all of these indicators, that the value of high-end relief pitching has risen to an all-time high.
This offseason the starting pitching market is incredibly barren. The best starting pitcher available is probably Jason Hammel, who was a successful fifth starter during the 2016 season. On the other hand, three of the best relief pitchers in the game are free agents. Each one of them is going to get paid. This will likely skew how teams value an elite bullpen compared to an elite starting rotation. With the opportunity to meaningfully improve only one of the two this offseason, teams are naturally going to end up favoring an elite bullpen.
For the sake of argument, let’s consider an even field. If teams are given free rein of acquiring starting and relief pitching talent, which should they value more? Should they try to build the best bullpen possible while punting on starting pitching? Should they build an incredible rotation and hand the ball over to a subpar bullpen?
For almost all of baseball history, perhaps even now, starting pitchers have been treated as the better and more valuable players. They are relied on for far more innings than their relief counterparts. More innings per game leads to more innings season long and more wear and tear on their arms. It takes special talents to undergo season after season of nearly 200 innings per year. Most pitching prospects begin as starting pitchers. Those that fail are then moved into relief roles. This is the case for even some of the best relievers in baseball, like Andrew Miller and Aroldis Chapman. It seems as though starting pitchers are simply better than relievers. This is most likely true.
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The general belief is that any one of the best starting pitchers in baseball could move into a relief role and become the best reliever. The best starting pitchers have great stuff, even when stretched out over many innings, so it follows that their stuff would be incredible in shortened appearances.
But the bigger question is not about who is better between starting pitchers and bullpens. The question is whether a team should choose an elite bullpen over an elite starting rotation. The answer, however, is heavily related to the relationship between starters and relievers.
A starting rotation over the course of a season provides around 900 innings pitched (average of 5.2 IP per start). An elite starting rotation would provide closer to 950 innings. The Cubs’ rotation was one of the best in baseball this year. They got 943 innings from their five main starting pitchers. That means relievers will pitch 508 innings per season on a team with an elite starting group. This begs the question of which is more valuable: quantity of innings or quality of innings?
Relievers, especially the best ones, pitch in the seventh, eighth, and ninth innings. When the team is ahead, those innings tend to be high stress and high leverage. Getting three outs in the ninth inning is agreed on to be more difficult than in the first inning. But is getting those final three outs more valuable than getting the first 20 or so outs?
Answers to this question will vary. Some fans, analysts, and front office members believe that having the best bullpen will naturally lead to a winning team. Those final innings are much more valuable to them, as long as their rotation is still good enough to skate by. Others think that a rotation is far more valuable.
I tend to side with the latter group. While the Royals last year and Indians this year showed that postseason success can be moved along by a great bullpen, the Yankees this year are a good argument on the opposite end. They had one of the best back-ends of a bullpen ever with Dellin Betances, Andrew Miller, and Aroldis Chapman. And yet they were unable to win games when all three were on the team. They simply failed to hand the ball to those guys with the lead.
The Cubs and Mets, on the other hand, have built great rotations and seen great success. The downside of a great pitching staff is the possibility of injuries, which the Mets endured their fair share of in 2016. However, that is not rotation or bullpen specific. Injuries to a rotation can hurt a team more than injuries to a bullpen, based simply on the number of innings lost. But if we can assume that no injuries occur (this is a dream world scenario), having a great starting rotation is far superior to a great bullpen.
Starters lay the groundwork in games and in postseason series. The Indians would not have gotten where they did without Andrew Miller. They also wouldn’t have made it where they did without Corey Kluber. Perhaps the best solution is somewhere in the middle. If the choice is black and white, teams should choose an elite rotation. Those pitchers can provide key innings over a 162-game season, and be vital in a championship run. The proof is in the Cubs coming back from a 3-1 deficit thanks to their three Cy Young level pitchers.