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The Mariners aren’t the first team built on a run differential-beating bullpen

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We would all prefer the M’s have a staff of aces, but the way Seattle is winning has been done many times before.

MLB: Detroit Tigers at Seattle Mariners Joe Nicholson-USA TODAY Sports

Can teams be built to cheat probability? Seattle’s league-leading 15 victories in one-run games has felt like the story of the season. The spectacular late-game heroism has been bad for my heart rate and sleep schedule, but excellent for Seattle’s playoff chances. If Seattle were to simply go .500 for the remainder of the season they’d earn 87-88 wins, likely enough to earn a Wild Card spot in a top-heavy American League. They must get more out of their offense, but right now they’re surviving by the dominance of their bullpen. That’s a style of victory we’ve seen elude the expectations of Pythagoras before.

Through Tuesday morning the Mariners rank 8th in Bullpen ERA, as well as 7th by FIP and 4th by fWAR. It’s been surreal to see Seattle amidst the “elite” of the AL in the standings, but elite is exactly how the Mariners’ bullpen should be described based on their peripherals thus far. Just the Yankees and Astros lead Seattle by K-BB%, and both the addition of Álex Colomé and recent mechanical improvement of Juan Nicasio should only further solidify the back end. It’s that brilliance that could allow the Mariners to finally bring the playoff rains to the Pacific Northwest.

These Mariners have been remarkable escape artists, but they’re following a deer trail many teams have tread to avoid the precipice of expected win/loss. Over the past 30 years, 18 teams have maintained a winning percentage of .650 or better in one-run games over a full season, and it’s only become more common as teams have leaned more heavily on their bullpens.

One-Run Game Magic Teams

Year & Team One-Run Game W/L Overall W/L Pythag W/L Bullpen ERA rank
Year & Team One-Run Game W/L Overall W/L Pythag W/L Bullpen ERA rank
2016 TEX 36-11 95-67 82-80 25th
2012 BAL 29-9 93-69 82-80 5th
2003 SFG 28-12 100-61 93-68 5th
2002 OAK 32-14 103-59 96-66 16th
2002 LAD 33-15 92-70 89-73 7th
2001 SEA 26-12 116-46 109-53 1st
2015 PIT 36-17 98-64 93-69 1st
1998 NYY 21-10 114-48 108-54 6th
2015 LAA 35-17 85-77 79-83 18th
2004 LAD 32-16 93-69 89-73 2nd
1995 CLE 28-14 100-44 93-51 2nd
1987 MON 28-14 91-71 83-79 2nd
2012 CLE 24-12 68-94 64-98 23rd
2016 NYY 24-12 84-78 79-83 16th
2006 TOR 20-10 87-75 86-76 11th
2018 SEA 16-8 33-20 28-25 8th
2006 NYM 31-16 97-65 91-71 2nd
2012 ATL 25-13 94-68 92-70 2nd
2013 NYY 30-16 85-77 79-83 20th
Teams sorted by W/L% in one-run games Baseball-Reference/Play Index

By and large, the teams who have best exceeded their run differential and excelled in one-run games have been those with dominant results from their bullpens. A few outliers exist, like the infamous 2016 Rangers and the otherwise-terrible 2012 Cleveland, but most teams who rank poorly on the whole have individual dominance to thank. The 2002-2004 Dodgers were privy to perhaps the most dominant three-year stretch of any individual reliever in prime Eric Gagne, which meant any late-inning lead was a lock. Similarly, the Yankees frequent this list despite sub-elite bullpens overall thanks to Mariano Rivera and various strong setup men.

Prior to the acquisition of Colomé, Seattle seemed to fall in that second outlier group. They boasted a lights-out closer and some good setup options, but saw their overall numbers dragged down by the innings-eaters in games that the starters failed to keep within reach to begin with. Now, however, Seattle is rolling with a healthy Ryan Cook, a refined James Pazos, and a no-longer-a-Met Chasen Bradford, Seattle has three decent options middle/long relief options, as well as Marc Rzepczynski. With a high leverage group of Nicasio, Colomé, a soon-to-return Nick Vincent, and of course Edwin Díaz, nearly every lead is safe, and small deficits can remain within reach.

Bullpens are, by their small sample nature, volatile. This could fall apart numerous ways, including injury, bad luck, or simple ineffectiveness. But while the Mariners pathway to victory so far has been atypical, it’s far from unprecedented. If the Mariners make the playoffs this year, it will be the most stressful style of baseball imaginable, but they’re built, in theory, to sustain it.

I’m just sure not we are.