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Major League Baseball's 2021 postseason rolls on today, with the American League Division Series between the Chicago White Sox and Houston Astros and the Boston Red Sox and Tampa Bay Rays kicking off.

Part of the appeal of the playoffs is the tension that comes with high stakes and championship opportunities. But not all October tension is created equally. Some fan bases are going to be sweating out the final few innings of every contest their team plays, uncertain if their bullpen will be able to secure a potentially pivotal victory.

With that in mind, we tried to quantify bullpen anxiety by turning to two FanGraphs measures: shutdowns and meltdowns. Both are derived from Win Probability Added and attempt to tell a story about how much a bullpen contributed to a win or loss. For our purposes, we took each playoff team's ratio of shutdowns to meltdowns. The higher the number, the more the bullpen contributed to its team's odds of winning.

Below, you'll find the eight remaining playoff teams ranked in descending order of that number. The teams who appear near the top are the ones who can feel most confident in their relief corps; those near the bottom, conversely, could be in for some long October nights. As always, keep in mind that this is for entertainment purposes only, and that you should dismiss any metric that does not conform to your preconceived notions.

8. Giants (SD/MD ratio: 2.3)

It shouldn't come as a surprise that the team with the best record happened to have a good, reliable bullpen. The Giants had seven relievers make at least 25 appearances this season, and only two of them (closer Jake McGee and Jarlín García) had double-digit meltdowns. Rubber-armed setup man Tyler Rogers deserves a special mention here, as he compiled a 43-to-6 shutdown-to-meltdown ratio. Keep an eye on rookie right-hander Camilo Doval. He has a nasty slider that generated a 40 percent whiff rate during the regular season, as well as an upper-90s cutter.

7. Dodgers (SD/MD ratio: 2.2)

Again, if you win as many games as the Dodgers did, you probably have a steady relief corps. Dodgers fans can be forgiven if they're skeptical about Kenley Jansen. He still suppressed contact at an elite level, but he also posted a career-worst walk rate and saw his velocity waver throughout the season. Nevertheless, Jansen and setup man Blake Treinen combined for 75 shutdowns versus 19 meltdowns, suggesting they're more than capable of taking care of business. Some other names worth knowing in the Dodgers bullpen include Joe Kelly, who had a resurgent season; Corey Knebel; and Alex Vesia, a little lefty acquired from the Marlins whose fastball plays much quicker than its velocity because of its rise, its extension, and its plane to the top of the zone. 

6. Brewers (SD/MD ratio: 1.9)

The Brewers' bullpen has become a staple of their recent postseason runs. Closer Josh Hader posted a 37-to-3 shutdown-to-meltdown ratio this season, but he won't have his usual setup man Devin Williams serving as a bridge after Williams broke his hand punching a wall. Milwaukee still has a couple of familiar names in their bullpen -- left-hander Brent Suter, he of the prehistoric bird of prey wingspan, and veteran closer Brad Boxberger -- but prepare to be introduced to the next wave of Brewers relievers, including lefty Aaron Ashby and slider-pumping righty Jake Cousins. Given Williams' injury, it would be fair to mentally bump Milwaukee down a peg or two.

5. Rays (SD/MD ratio: 1.9)

With the exception of a few holdovers, like Pete Fairbanks, the Rays have essentially remade their bullpen from last October. Tampa Bay had 14 relievers record at least one save this season, none on the active roster had more than sinker-slider right-hander Andrew Kittredge, who notched eight. The Rays acquired spin monster J.P. Feyereisen in the Willy Adames trade, then picked up slider maestro Matt Wisler off waivers. Colin McHugh has also proven to be one of the better values of the winter, having recorded 64 innings of 1.55 ERA ball in exchange for a paltry $1.8 million. 

4. Red Sox (SD/MD ratio: 1.9)

As with the Rays, the Red Sox had a lot of pitchers get in on the save action: 10 in total, including staff leader Matt Barnes. Barnes hasn't recorded a save since early August because of some turbulence that is captured by his 23-to-12 shutdown-to-meltdown ratio. The Red Sox have instead turned to Hansel Robles in the ninth. Robles has been good, but it's a fair guess as to when his gopher-ball tendencies resurface. Rule 5 pick Garrett Whitlock, plucked from the Yankees system, is the one worth watching here. He just returned from injury on the final day of the season, but over the course of the year he compiled a 1.96 ERA and a 4.76 strikeout-to-walk ratio in 73 frames.

3. Braves (SD/MD ratio: 1.8)

Although it feels like Braves closer Will Smith is perpetually walking the tightrope, his 39-to-11 shutdown-to-meltdown ratio is respectable enough. The Braves have had more issues with A.J. Minter, whose 21-to-14 ratio leaves a lot to be desired. If there's one potential difference maker in the Braves postseason bullpen, it's rookie Spencer Strider. He has a top-notch fastball that helped him tear through three levels and counting this season. The only question is how much trust the Braves have in him, seeing as how he's made all of three career appearances above the Double-A level.

2. White Sox (SD/MD ratio: 1.4)

The White Sox being this close to the bottom of the list is, by far, the biggest surprise here. On paper, the White Sox would appear to have a lockdown bullpen with veteran late-inning types like Liam Hendriks and Craig Kimbrel and up-and-comers like Michael Kopech and Garrett Crochet. In reality -- or, at least, through the reality this metric captures -- they've had their troubles. To be fair, three pitchers in particular are responsible for Chicago's woes: Aaron Bummer, José Ruiz, and Codi Heuer (since traded to the Cubs in the Kimbrel deal). Those three combined for 34 meltdowns versus 32 shutdowns. If you removed that trio from the equation, the White Sox's unit-wide shutdown-to-meltdown ratio would improve from 1.4 to 1.7. That's still not great, but it speaks to the anchoring effect Bummer, Ruiz, and Heuer have had. 

1. Astros (SD/MD ratio: 1.2)

According to our basic little metric, no team's fan base should be more leery about a late lead than the Astros. Put another way, Houston's bullpen had as many meltdowns (97) as the Phillies -- with significantly fewer shutdowns. The top offenders were Ryne Stanek, Brooks Raley, Bryan Abreu, and Blake Taylor, each of whom recorded double-digit meltdowns. Even Phil Maton and Yimi Garcia, two in-season acquisitions, combined for seven shutdowns versus 12 meltdowns, suggesting general manager James Click didn't entirely solve his problem in July. The Astros are a trendy pick to make it to another World Series. If they don't, their bullpen could be why.