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Carson Smith and the Sustainability of a Breakout Reliever

Today's elite relievers are breaking out and staying there.

Bruce Kluckhohn-USA TODAY Sports

Carson Smith had a breakout season in 2015. He became the eighth reliever in Mariners history, and the first in nearly 10 years, to drop anchor on the glistening and remote shores of the prestigious 2-WAR Club:

Whoa, a Bobby Ayala sighting. Did you know that he has the 4th most fWAR of any Mariner reliever? It’s true, and that’s the thing about relievers. The fact that Bobby Ayala ranks in the 99th percentile for reliever WAR on a 40-year-old team symbolizes how difficult it is to sustain a high level of performance out of the bullpen. Had Smith remained a Mariner, he may have passed Ayala in 2017. Then again, maybe not. Maybe never.

Whatever the future holds for Carson Smith, he was good enough in 2015 to make us uncomfortable when the Mariners traded him and his five years of team control to Boston. The trade itself has been analyzed extensively, and the general consensus is the Mariners received the slightly shorter end of the stick, particularly in comparison to the Ken Giles trade that followed. So, what motivated Jerry Dipoto to part with his bullpen ace for a relatively modest return?

The rote answer is "volatility," though it's worth mentioning that teams outside of Seattle have bucked conventional wisdom and are increasingly targeting shutdown relievers. Maybe they are doing so out of a greater understanding of the value of late-inning relief. Maybe they just have money to spend. Perhaps teams are simply plagiarizing the Royals.

But there is one more potential driving force I want to show you. Today’s elite relievers are not as volatile as they once were.

Using Smith’s breakout season as our template (this is where all of this digging around began), we can group a handful of comparatively young breakout relievers, and see how they fared in their next five seasons. The idea here is to use a peer group to estimate the value Smith will provide through 2020.

Breakout Season Criteria:

/// 1995-2010

Today's bullpens are structured and used differently than they were even a few decades ago. In 1989, 13 relievers pitched 100 or more innings. No reliever has done so since 1996, and only Dellin Betances topped 80 innings in 2015. For the sake of convenience, let's only examine relievers from 1995 or later, the last season in which a reliever topped the 100-inning mark.

/// Between ages 21-26.

Setting the maximum breakout age at 26 ensures that we won't have our sample muddled by older performers. We'll be looking at five-year performance, and conveniently, age 31 is the final season an average reliever stays within one mile per hour of his peak average fastball velocity. Carson Smith will be days shy of his 31st birthday at the conclusion of his projected cost-controlled years.

/// Posted a minimum of 1.5 WAR and/or 1.5 WAR per 70 IP with a minimum of 40 IP.

WAR may not be the best tool for evaluating relievers, but we're not voting for the Rolaids Relief Award: we're simply trying to identify late-inning hurlers with similar value. For reference, 1.5 WAR is typically a top-20 season for a relief pitcher, and the most valuable relievers in history not named Mariano Rivera averaged about 1.5 WAR per season. Smith racked up 2.1 WAR last season.

Sustainability Criteria:

/// Seasons 2-6 from the breakout group.


/// Relievers who switched to starters during seasons 1-6 and swingmen who did both.


51 pitchers, 306 seasons, 15,592 appearances and 16,216 innings pitched.

Before looking at how these pitchers performed over a period of six seasons, here is the average breakout season from our list of 51 comparable relievers to confirm an essence of Carson Smith’s breakout season:

Smith's k% is much better, but that's partly a function of the high strikeout environment he pitched in, and his IP, ERA- and FIP-, WAR and average age are comparable to the cohort. Below we can see how those relievers performed over their next five seasons:

The average ERA- and FIP- for a reliever from 1995-2010 was 95 and 98, respectively, so our group of breakout relievers remained above average for the duration of their "cost-controlled" years. That’s the good news. The bad news is they lost nearly 50% of their breakout value (Brk%) in seasons two and three before falling off a second cliff. When examining reliever WAR, it’s important to remember that leverage is baked into the equation. So, as our group of pitchers gradually pitched less effectively, they pitched in fewer high leverage situations, which in turn further suppressed their WAR at a greater rate than their ERA- and FIP- might otherwise suggest.

Another red flag is the attrition rate in our sample, highlighted by the M.I.A. column. This represents entire seasons lost to Tommy John surgery, retirement, a demotion, etc. As a group, these relievers lost 10.6% of their total cost-controlled seasons. The impact of injuries and declining skill over time are also reflected in the average number of games and innings for our sample (M.I.A. pitchers were not included in any of the averages or rate stats).

Next, let's isolate the relievers from this group who were most like Carson Smith. Here, we'll impose tighter restrictions for IP, ERA- and FIP-:

Naturally, these pitchers performed very similar to Smith. Their collective ERA- and FIP- are closely aligned and the K% would be nearly identical if we adjusted for era. Here is how they performed over a six-year stretch:

Undoubtedly, this group of relievers performed better over their first three seasons. Perhaps the most interesting points are the rapid decline in K%, and how this group is nearly indistinguishable from our initial set by season four. They were more durable, however, losing only 6.7% of their total cost-controlled seasons.

How about the breakout relievers from the first group who were even EVEN more like Smith, but in a different way? Here, we'll only select comparable relievers who also threw:

  • 90 mph or harder
  • A slider within 10 mph of their average fastball
  • Their slider 30% of the time or more

This sample features only 12 relievers, and the numbers aren’t aligned as closely with Smith's performance last year. That's ok for our purposes: here, we just want to isolate how slider-heavy relievers fared over time:

Ouch. While the first two groups held strong in seasons two and three before bottoming out in season four, this group plummets in season three. A more dramatic innings decline and an 18.3% M.I.A. also weakly supports the conventional wisdom that slider-heavy relievers are at a greater risk of injury than other hurlers. It's worth noting that Carson Smith threw a very high percentage of hard sliders (45%) in 2015.

That’s an awful lot of stuff to consider all at once, so here are the three comp sets combined into a single weighted 3-2-1 projection, with the heavier weights representing Carson Smith’s most similar comps in terms of performance and slider usage:

Based on the six-year performances of comparable pitchers, it appears that retaining a premium young reliever is a gamble, and particularly in seasons 3-6 following a breakout performance. So why not cash in, right? Well, take a look at the relievers who didn’t qualify for our initial samples, because they broke out sometime between 2011-2015:

These are today’s premium relievers. Thirty of them have pitched at least one season, and half are entering their final two years of team control. Barring a major collapse from this group over the next several years, the delta is glaring: baseball’s best relievers are sustaining their health and productivity in a way that they simply weren't doing before. Why? I have a theory: check out the IP column, and compare it to our initial 51-pitcher set. The young, shutdown hero who pitches multiple innings per appearance has become a thing of the past as teams are wisely milking more long term value from their most volatile assets and appear to be saving young pitchers' careers in the process.

Carson Smith averaged exactly one inning per appearance in 2015, which, given the table above, bodes well. He also throws a ton of sliders and has an unorthodox delivery, so who knows. Relievers will always be volatile due to the stress of pitching at max effort and the small sample sizes inherent in their line of work. But if the Mariners are lucky enough to develop another lights-out reliever in 2016, let’s hope they treat him well and maybe keep him around for another season or two.

Go M’s.