Are relief pitchers replaceable? Signs point to yes

As fanatics, we’re all prone to misevaluations based on our own idiosyncrasies, personal player preferences, and in some cases, our emotions.

A mistake many fans make (as well as some teams’ front offices) is overestimating the importance of individual relief pitchers. This isn’t to say that relief pitching as a whole, on a team level isn’t crucial, because it is. The reality, however, is that individual relief pitchers — even very good ones — are more replaceable than most of us realize.

Our emotions cause us to overlook a few facts, probably because when relief pitchers screw up it usually means the end of the game in a less than desirous manner. First, over the course of 162 games, an individual reliever has only a negligible impact on a team’s record. Second, when the starting pitcher screws up in the second inning, it’s just as bad as when your favorite set up guy blows up the eighth inning. It just doesn’t seem that way because of the sequence of events, as we’re more likely to be steamed by the most recent.

If you’re skeptical about any of the above, let’s take a look at the value of relief pitchers over the course of 162 games, compared to the respective values of starting pitchers and position players. Here are the number of individual seasons of greater than three WAR and greater than four WAR for each role, since 2011:

There’s much to unpack there, but the take-home is that on average fewer than three relievers per season produce more than three WAR, league-wide. The best of the best relievers aren’t delivering as much value as a good (not great) position player or most teams’ second starter. And that’s a reliever having an otherworldly season — we’ll talk about closer to human performance in a moment.

If you’re curious as to how much stock teams put into those numbers, here’s a reminder: The past four World Series were all closed out by starters pitching in relief, while some very good relievers watched from the bullpen. That means it’s not just an accumulation of innings leading to higher WAR totals — starters are simply better pitchers than relievers in most cases.

We need to look no further than the 2021 Yankees to see this play out in real-time on a micro-level. Zack Britton, who was one of the two relief pitchers in the table above to top four WAR in a season, was lost to the Yankees due to elbow surgery in March. Obviously, Britton is a very good relief pitcher. Most measurements we use for relievers such as K%, K%-BB%, and FIP don’t tell the whole story with Britton, as he allows a good percentage of balls to be put into play. His ability to keep the ball in the park, and specifically to keep it on the ground, are on elite levels. In 2019, his only full season as a Yankee, Britton’s HR% was more than three times lower than the league average, and his GB/FB ratio was more than 12 times better than league average. It’s because of those skills that losing him for the start of the season was considered a big one to the Yankees by most.

Even though Britton has been very good as a Yankee, his value comes out to between 1.5 and 2.0 WAR per 162 games based on his past performance. That’s not insignificant — but it is replaceable. Even back in March, it was reasonable to assume that whoever his replacement(s) were, even if not as good as Britton, would pick up some of that missed WAR. So we’re really talking about a single team win per season over 162 without Britton.

If you’ve been watching this season, I probably don’t need to tell you how the Yankees’ bullpen has fared in Britton’s absence, but let’s review for clarity’s sake:

The Yankees’ bullpen has the lowest percentage of inherited runners scoring and the best WHIP in MLB. They’re second in ERA, K/BB ratio, and outs per game in relief, while being one of only two teams without a blown save. If you’re planning on pulling the small sample size card on me, consider two things: First, as mentioned above, even over the course of a full season we’re talking about a minimal effect on wins and losses if an individual reliever or two begins to struggle. Second, of the staff’s seven most-used relievers this season, five have proven track records. The others are Jonathan Loaisiga, whose success can’t be surprising, and Lucas Luetge, who isn’t likely to log a ton of innings.

You never want to see a player get hurt, and not being able to watch one as good as Britton can be frustrating to fans. In the 162-game scheme, however, his absence is as manageable as it would be for virtually every relief pitcher. If a player for whom four or five WAR is an “OK” season, but if things are right they’re worth seven or eight (See; Cole. See also; Judge, LeMahieu, Stanton) gets injured — then you panic.