Bullpens continue to become more influential. While the ball might change and we might have seen the use of defensive shifts peak -- which declined in number for the first time in 2017 -- the bullpen's significance continues to grow with each passing season.
Relievers accounted for an MLB-record 38.1 percent of total innings thrown in 2017, up 3 percentage points (35.2 percent) and 1,200 innings from just 10 years earlier. In 2017, relievers surpassed their previous record for workload -- set in 2016 -- by 578 innings. Thirty years earlier, bullpens accounted for 31.8 percent of innings, and 50 years earlier bullpens accounted for 26 percent of innings.
The game warps even more toward the bullpen in the postseason. In the 2017 playoffs, starters accounted for 358 postseason innings, while relievers accounted for 310 -- or 46.4 percent of innings.
Starter workload continues to decrease as the game continues to become more extreme in a number of related areas, from role specialization to injury rates.
Clubs have become more creative in employing and leveraging their best bullpen arms and in limiting starters' exposure to opposing lineups. In 2016, the Cleveland Indians were lauded from moving Andrew Miller into higher-leverage situations before the ninth inning. Last October, the Los Angeles Dodgers aggressively limited their starters, such as Rich Hill, to two times through opposing lineups before turning over the game to a talented bullpen.
Bullpens arms are also being valued differently. They're becoming relatively more expensive. This offseason we're seeing fascinating strategies when it comes to bullpen-building. Some teams, such as the Rockies and Phillies, have spent significant money on relatively anonymous relief help while other clubs, including the Dodgers, have let an impact reliever walk away and seem content to find the next pop-up reliever to replace him. (In letting Brandon Morrow walk, the Dodgers are likely also trying to stay under the more punitive luxury tax.) Teams are in agreement that bullpens are more significant, but is there a right way to build a bullpen?