How sabermetric trends could affect the Cardinals: the bullpen

Much has already been written this offseason about the Cardinals bullpen. There are specific players many believe should be targeted: Juan Nicasio, Mike Minor, Mark Appel, Derek Holland, and more. There are also strategies for improving the bullpen that could be used: shopping at the bottom of the market and looking for upside as well as compiling a plethora of arms instead of a valued few. But what do recent statistical trends tell us not only about the best players to acquire, but also about in game strategy? What are the best teams good at and in which areas do they get away with being sub par?

Certainly, there are trends that will always lead to success—strike out more hitters, walk fewer batters, leave more runners on base. An interesting note from these obvious trends comes from strikeouts, which have been on the rise for a few years now across the league and especially with bullpens. From 2000 to 2015, four bullpens achieved a rate of more than ten strikeouts per nine innings. Since then, it has been done six times and the teams have been successful. All four teams to achieve this rate in 2017 made the playoffs, including the eventual World Series Champion Astros.

The Cardinals have improved on this front in each of the past three years, but they have still fallen short of the elite ten strikeouts per nine innings level. In fact, they have not even reached nine strikeouts per nine innings as a team. This does not exclude them from success by any means. It does, however, suggest a realistic and logical area for improvement—acquire more strikeout pitchers.

The winner of the World Series has had bullpen averaging just over nine strikeouts per nine innings over the last five years. That is not to say that a team averaging less cannot be successful. The 2014 Giants are a large outlier. The San Fransisco bullpen posted a rate of 7.38 Ks per nine innings. That was four years ago, and the number has only increased since. This is not a stand alone measure of success, but it is a trend that makes sense. And with the game moving more toward strikeouts, why shouldn’t the Cardinals join the club?

A lower walk rate does not correlate to success as strongly as a high strikeout rate. Without question, organizations do not make personnel decisions based on one statistic. It is easy, though, to skip over a player who has an elevated walk rate. This pattern suggests that might not be such a large issue. The main takeaway here is not that walking more batters is insignificant, but rather that the strikeout really does correlate to a strong bullpen.

As mentioned above, the Cardinals lost Trevor Rosenthal, a pitcher who has averaged well above 10 strikeouts per nine innings for years. In 2017, he averaged over 14 strikeouts per nine innings—a phenomenal number that can't be easily replaced. The Cardinals do not currently have a reliever with a strikeout rate above ten. Alex Reyes is one option to fill this void, but his time in the bullpen is and will be limited. Juan Nicasio is another player who has managed a rate above ten in the past and is a player many want to bring back.

The increasing rate of strikeouts is a trend that is hard to miss. Teams that have adjusted to build pitching staffs around this idea have been largely successful, especially in the postseason. It is not the only way to win, but at this point, it is common sense backed up by numerical evidence. The Cardinals, with Mike Maddux at the helm, would do well to jump on board.