Is a lockdown bullpen the most important ingredient of a World Series contender?

This past offseason, three of the seven largest contracts were given to closers.

That’s right. Aroldis Chapman, Kenley Jansen and Mark Melancon, who only pitch an inning most nights and typically throw less than 20 pitches signed bigger contracts than everyday players like Mark Trumbo, Jose Bautista and Josh Reddick.

After a postseason where Andrew Miller turned the world upside down by pitching 15 scoreless innings before allowing a run as a setup man, the importance of bullpen depth has become a trend in MLB. With Miller and closer Cody Allen, the Cleveland Indians surged to the World Series after sweeping the Boston Red Sox and Toronto Blue Jays.

It wasn’t just the Indians who used a dominant bullpen to make it to the World Series. In 2014 and 2015, the Kansas City Royals made a habit of ending games after six innings.

In 2014, similar to the 2016 Indians, the Royals did not lose a game on the way to the World Series. During that eight game stretch, the trio of Kelvin Herrera, Wade Davis and Greg Holland combined to only allow five earned runs across 40.1 innings.

The next year, Kansas City finished the regular season second in MLB in bullpen ERA (2.72), continuing the success from the previous season. In the postseason without Holland, Davis and Herrera only allowed one run over 24.1 innings and delivered a championship.

Seemingly, the route to the World Series lies in strong bullpen pitching.

Not so for the 2015 Pirates. Pittsburgh led MLB in bullpen ERA (2.67) thanks to strong performances by Mark Melancon, Joakim Soria and Watson, yet lost to the Chicago Cubs in the Wild Card Game.

This brings us to the counter-argument.

As good as the Royals and Indians bullpens were, a strong relief corps does not guarantee success. The 2016 Cubs are proof that that strong rotation is just as, if not more, important.

With Jake Arrieta, Jon Lester and Kyle Hendricks leading the way, the Cubs led MLB in starting pitcher ERA (2.96) last season. It wasn’t just that the Cubs’ starters pitched well, they went deep into games too; Chicago finished second in MLB in innings pitched by starting pitchers (989).

The Cubs had a stellar bullpen as well (3.56 ERA) but it was not as needed with the effectiveness and durability of its starters. The 2015 Royals finished 24th in MLB with 912.2 innings pitched by starting pitchers. Kansas city needed it bullpen.

Similarly, the San Francisco Giants had a better starting rotation than bullpen. In 2010 and 2012, the Giants finished among the 10 best teams in starting pitcher ERA en route to two world championships.

However, in 2014, the Giants actually had a better bullpen ERA (3.01) than starter ERA (3.74). Part of that is because no starter that made at least 15 starts finished with an ERA below 3.00 besides Madison Bumgarner (2.98).

In the end, it depends on the team. The Cubs were a top 10 team in ERA for starters and relievers, so they had both. History says that both have to be pretty strong to win a title, but there are outliers like the Royals, who finished 22nd out of 30 MLB teams in starter ERA in 2015 yet have a ring.