Almost everything in baseball is cyclical, including the perceived value of top relief pitchers. When the one-inning closer was new, award voters enamored of gaudy rate stats and save totals lavished six Cy Youngs and three AL MVP awards on relievers from 1979 to 1992. Since then, conventional wisdom has moved toward the idea that all relievers — even great ones — are failed starting pitchers, and that the quantity of innings thrown by starters outweighs the quality of innings thrown by closers. Mariano Rivera, the greatest reliever ever, never won a Cy Young, and since Eric Gagne in 2003, no relief pitcher has.
However, the enormous price paid for relievers Andrew Miller, Aroldis Chapman, and Will Smith at the trade deadline suggests that that pendulum might be swinging back to where it was 30 years ago.
In the American League this year, the closest thing to a favorite, Corey Kluber, has a 145 ERA+ through 157 innings, good for 4.0 WAR through 23 starts. Extrapolating that out to 33 starts, Kluber’s on pace for 5.74 WAR. R.A. Dickey won the Cy Young with a 5.8-win season in 2012, but, at his current pace, Kluber would be in the discussion for the worst season by a Cy Young winner since Bartolo Colón (4.0 WAR) in 2005. Kluber would be the first pitcher with an ERA over 3.00 to win it since C.C. Sabathia in 2007, when the offensive environment was much more hostile to pitchers.
While Kluber, Aaron Sanchez, José Quintana, and whoever your Cy Young favorite might be are all having great seasons, there still really isn’t an inspiring starting pitcher to rally behind. Instead, the American League has a bumper crop of stellar relief pitchers, led by Baltimore’s Zach Britton.
I don’t expect Britton to win the Cy Young, but if you wanted to make the case for Britton over Kluber, here’s how you’d do it.
The argument that starters are inherently more valuable than relievers is based on two assumptions: First, much of Kluber’s value comes from the sheer size of his workload; he’s pitched over three times as many innings as Britton this year. Second, since starting is more difficult than relieving, almost everyone who can start does, leaving relievers as cast-offs. In short, Kluber could probably do what Britton does, but Britton couldn’t do what Kluber does. We know this because Britton made 46 starts earlier in his career, and he was pretty bad: 4.86 ERA, opponent slash line of .279/.353/.407.
Now, the second assumption is very important for scouting, but totally irrelevant to the Cy Young discussion. Awards are necessarily backward-looking. They’re based on what actually happened, not what could have happened. The question is not whether Britton could be Kluber, but whether Britton provided more value than Kluber, and that goes back to the first assumption: Does Kluber’s three-to-one advantage in innings actually make him more valuable than Britton?
WAR says yes: Kluber’s 4.0 is better than Britton’s 2.9, which is closer than any reliever ever ought to be to his league’s top starting pitcher, but is still a considerable gap.
The argument doesn’t end there, though. Compared to other elite relievers, Britton is good in sort of a weird way. He doesn’t post the gaudy strikeout numbers we expect from Miller, Chapman, or Craig Kimbrel. In fact, his K/BB ratio is actually slightly worse than Kluber’s, though he still strikes out 30.9 percent of batters faced to Kluber’s 25.2.
Britton’s very good at avoiding contact, but what makes him special is what happens when batters actually do make contact. Among all big league pitchers with a minimum of 40 innings pitched, Britton allows the lowest hard-contact rate (14.6 percent) and the second-lowest line drive rate (12 percent). (Out of 292 pitchers, Kluber is 123rd in line drive rate at 20 percent and 53rd in hard contact rate at 27.2 percent.) Britton’s sinker allows him to keep the ball on the deck better than anyone else in the game; he allows 9.56 ground balls for every fly ball, almost three times better than second-place Sam Dyson.
Softly hit balls on the ground are incredibly likely to turn into outs, and ground balls account for 79.6 percent of the balls Britton allows to be put into play. That’s why he’s allowed only one home run all year and — here’s the kind of easy-to-remember stat none of the AL starters have — only three earned runs of any kind. Despite pitching in front of roughly equivalent defenses (Cleveland is 12th in Baseball Prospectus’s park-adjusted defensive efficiency, Baltimore 14th), Britton is allowing an opponent BABIP of .213, compared to .270 for Kluber. Between the slight advantage in keeping balls out of play and the huge advantage in converting them to outs if they do get hit, Britton’s got a massive edge in per-inning performance.
Britton has a 0.56 ERA, and a 793 ERA+, with an opponent slash line of .145/.217/.200. Compare that to Kluber: 3.21 ERA, 145 ERA+, opponent slash line of .214/.263/.336.
Does that make up for a three-to-one advantage in innings? Probably not. Britton allows about one-sixth as many runs as Kluber, but he records only about three more outs and allows 13 fewer total bases per 100 batters faced.
Yet, Britton doesn’t have to be three times better on a per-inning basis, because the innings he throws are far more important than Kluber’s. The whole point of a closer is to bring in your best pitcher to pitch the most important innings. The average leverage index (pLI) of a Britton appearance is 1.78 , the 15th-highest mark in baseball this year. Kluber, by contrast, is a 0.82 (average is 1.0). So, essentially, the outs Britton gets have almost twice the impact on win probability compared to an average out, while Kluber, like most starting pitchers, tends to pitch in slightly below-average situations in terms of leverage.
The resulting difference in win probability is enormous. Britton’s cumulative WPA is 4.29, which blows away the field, including all other relievers and the National League’s best starting pitchers. At a WPA of 0.85, Kluber might have pitched more innings, but Britton’s had a much bigger impact on his team’s chances to win.
If you trust Baseball-Reference’s WAR to balance quantity and quality, it says Kluber’s been about 38 percent more valuable without accounting for leverage. But accounting for leverage, Britton’s innings have been 117 percent more important than Kluber’s. Even if the numbers are a little crude, that’s the argument for the first closer Cy Young in 13 years.
Of course, this isn’t a bulletproof argument — a low BABIP and high WPA mean you’re pitching well, but they can also be influenced by factors outside the pitcher’s control, such as usage patterns, luck, and team defense. There are certain things Britton benefits from that he can’t control, in the same way a NASCAR driver doesn’t design his car or manage his pit stops, but Britton’s still the one behind the wheel.
Whether that matters is up to individual voters, but if ever there were a year for a one-inning closer to win the Cy Young, this is it.