Is having a negative run differential historically important in the MLB postseason?

When perusing the final standings on MLB.com, the only column that matters on October 3 is the one labeled Next Game. Unless you’ve dominated this season and have a first-round bye, a blank space means you started the offseason prematurely.

But something else catches the eye when looking at the Arizona Diamondbacks or the Miami Marlins, a red number in the run differential column. The D-backs’ red -14, for example, looks strange sandwiched between the green numbers of the National League West winning Los Angeles Dodgers and the San Diego Padres +104, a team notoriously missing from the 2023 MLB Postseason.

Famed baseball statistician and historian Bill James identified the correlation between run differential (runs scored minus runs allowed) and win-loss record. What he recognized is that some teams can overachieve with a negative run differential while others like the Padres or the +96 Chicago Cubs from this season can actually do worse than the run differential would suggest.

So is having a negative run differential that bad of a situation for a playoff team? Is it an indicator of success in October? Or is it more like a harbinger?

A total of 11 teams have made the postseason with a negative run differential. Two from this year and three from the pandemic-shortened season in 2020. The rest, coincidentally enough, came from either the NL or AL West.

It’s not a large sample size, but there are definite trends and a few outliers. 

Let’s take a dive into the history of negative run differential teams in the postseason…

The Good: 2007 Arizona Diamondbacks, -20 run differential

Insert meme of Spider-Man pointing at himself. The last division winner with a negative run differential is the same franchise as the most recent to make it.

Anyone remember these guys?

Today at @TheRattleAZ, I discuss 7 lovable players from a 2007 #Dbacks club that went farther than we could ever have imagined: https://t.co/gT0XF0IXSX pic.twitter.com/4KitaHaop7

— Jesse Friedman (@JesseNFriedman) April 16, 2020

The 2007 squad went 90-72 as the NL West winners and looked strong during the National League Division Series over the Chicago Cubs (+62). D-backs won Game 1 and trailed for only a half-inning in Game 2 on a Geovany Soto two-run homer run before immediately responding with a three-run shot by Chris Young to take the lead. It’s the only time Chicago held an advantage in the series. Following the first two wins at home, Arizona went into enemy territory to put down the Cubs for the sweep at Wrigley Field.

.@CY24_7 and @markdero7 flash back to facing each other in the 2007 NLDS between the @Dbacks and @Cubs! #MLBCentral pic.twitter.com/J5Sa0X2HD3

— MLB Network (@MLBNetwork) June 18, 2021

Next came the NL Championship Series against a team enjoying one of the hottest runs in baseball history. The Colorado Rockies (+102) won 13 of their final 14 games that season to force Game 163. Three runs in the bottom of the 13th vaulted the Rockies into the playoffs where their momentum added three more uncontested wins over the Philadelphia Phillies (+71).

The matchup of recent expansion franchises in the southwest was one-sided as Colorado extended Rocktober for another week, sweeping Arizona for their 21st win in 22 tries.

The Good: 2020 Miami Marlins, -41 run differential

Miami was one of three teams to make the expanded postseason following the 60-game shortened season. A total of 16 teams made the playoffs that year, and though the Toronto Blue Jays (-10) and Milwaukee Brewers (-17) were both the eighth-best team in their respective league, the Marlins at 31-29 were at least tied for a share of the final Wild Card.

Miami went to Wrigley Field and won the first two games for an easy sweep over the Cubs (+25). Other than a solo home run by Ian Happ against Sandy Alcantara in Game 1, the Cubs were held scoreless the remaining 17 innings at home. 

Marlins playoff appearances
1997: WS Champs
2003: WS Champs
2020: COVID season icons (lost in 2nd round)
2023: ????

— Céspedes Family BBQ (@CespedesBBQ) October 1, 2023

From there, the Marlins pitching turned into a pumpkin and the offensive horses into mice during the NLDS against Atlanta (+60). They managed to score five in Game 1 before being shutout in the next two games for the sweep.

The Bad: 1984 Kansas City Royals, -13 run differential

Six of the nine teams to play in the postseason with a negative run differential were swept in the first round. The 84-78 Royals are a part of that inauspicious group. If any club on this list so far can provide hope in a losing battle, it’s this one.

Kansas City went up against the eventual World Series winners in the Detroit Tigers (+186). They were outmatched against Jack Morris in Game 1 before being edged out in 11 innings in Game Two and, falling on the wrong side of a pitchers’ duel, lost 1-0 in Game Three. That’s not the hopeful part.

The next season, the Royals won the AL West again and had the postseason chutzpah to win the ALCS in seven and take down their cross-state rivals in the St. Louis Cardinals to win the 1985 World Series, their first in franchise history.

Today In 1985: The Kansas City #Royals win their first World Series championship, defeating the St. Louis Cardinals in seven games! #MLB #Baseball #TogetherRoyal #WorldSeries pic.twitter.com/o3YTzc7rYE

— Baseball by BSmile (@BSmile) October 27, 2022

The Hopeful Outlier: 1987 Minnesota Twins, -20 run differential

Back in the day, the concept of a Wild Card was scoffed at. You either win your division or start playing golf a month earlier. It wouldn’t be until the San Francisco Giants missed the postseason with 103 wins in 1993 that baseball smartened up and changed the system.

In the case of the 85-win Twins, who won the AL West when there were only two divisions, they wouldn’t have made the playoffs until the format added a second Wild Card as four teams from the AL East had better records. Coupled with the negative run differential and it seems Minnesota was probably one of the least qualified postseason teams of all-time.

Today In 1987: The Minnesota Twins win the World Series, defeating the St. Louis Cardinals in seven games! #MLB #MNTwins #WorldSeries pic.twitter.com/6dIDFSvaQ3

— Baseball by BSmile (@BSmile) October 25, 2022

And yet, these were rules at the time and Minnesota got the chance to extend their season in the ALCS against the Tigers (+161), the team with the best record in MLB that season. They disposed of Detroit in five games before going the full seven games against the NL’s best, the St. Louis Cardinals, to win the franchise’s first World Series since moving to Minnesota in 1961.