Regular-season showings affect the seedings for the postseason. But once you cross that threshold into October baseball, you’re on your own. In a short series, anything can happen -- and quite often does. One can never be sure which players will run hot or cold and which surprise stars seize the stage.

That’s why October history is littered with instances in which the so-called “better team” was not victorious.

What follows is a list of the top 10 upsets in MLB postseason history. While there certainly have been many other instances in which a plucky club spoiled people’s perceptions, this is a purely objective list determined by the winning percentage differentials between the winner and the loser.

Note: We're excluding the 2020 Astros' victories over the Twins (American League Wild Card Series) and A's (AL Division Series) because they came after a pandemic-shortened 60-game season.

1) 1906 World Series: White Sox (.616) defeat Cubs (.763) -- 147-point difference
The winning percentage gap between the American League and National League pennant-winners in 1906 is actually the largest for any World Series ever played. The Cubs, who put the “Tinker to Evers to Chance” poetry in motion and had Mordecai “Three-Finger” Brown on the mound, won 116 games, an NL record that still stands. The White Sox, meanwhile, were the “Hitless Wonders” having won 93 games despite a .228 team batting average. The Sox, though, stepped up in the clutch, battering Brown in Game 6 to become the first -- and far from the last -- underdog to capture the Fall Classic.

2) 2022 NLDS: Padres (.549) defeat Dodgers (.685) -- 136-point difference
The Dodgers weren’t just coming off their ninth NL West title in 10 years; they were coming off the highest win total (111) in the history of a franchise that dates back to the 1880s. Fourteen of those 111 wins had come against the Padres, who had been outscored in the regular-season series, 109-47. But the Padres had made a ridiculous number of major transactions -- including a particularly seismic swap for Juan Soto -- in an effort to keep pace with the mighty Dodgers. And after bouncing the 101-win Mets in the Wild Card Series, they saved their best effort for L.A.

3) 2001 ALCS: Yankees (.594) defeat Mariners (.716) -- 122-point difference
As proven by the 1906 Cubs and the 2001 Mariners, winning 116 games in the regular season is a terrible plan! In ’01, the Mariners enjoyed the arrival of Ichiro Suzuki and led the Majors in runs (927), stolen bases (174), on-base percentage (.360), ERA (3.54), shutouts (14) and WHIP (1.20). But then along came the Yankees, who, as three-time-defending World Series champs, hardly had the look and feel of a dark horse. Both clubs were coming off Division Series that went the distance, and the Yankees proved deeper and more resilient by taking the first two in Seattle to steal the home-field edge and, eventually, the series. The Yanks went on to an epic World Series with the D-backs, which they lost in seven games.

4) 2021 NLCS: Braves (.547) defeat Dodgers (.654) -- 107-point difference
These teams came out of two very different division races. The Dodgers won 106 games but fell one game shy of the 107-win Giants in an epic rivalry. The Braves, on the other hand, survived a slog of a season in the NL East, where, at times, it appeared nobody was interested in advancing. But the Braves went 37-19 down the stretch after adding a slew of outfielders at the Trade Deadline to account for the absence of injured MVP candidate Ronald Acuña Jr. And after dismissing the NL Central champion Brewers in the NLDS, they overwhelmed the mighty Dodgers, who had defeated them in this round one year earlier. Huge hits from both expected (Freddie Freeman) and less-expected (Eddie Rosario) sent the Braves to their first NL pennant since 1999.

5) 1973 NLCS: Mets (.509) defeat Reds (.611) -- 102-point difference
Just four years after their “Amazin’” run to glory in 1969, the Mets dismantled the Big Red Machine to set a still-standing record for the lowest winning percentage by a pennant winner in history. “Ya Gotta Believe!” was the Tug McGraw-crafted rallying cry, but finally getting healthy late in the season also helped. This was back when the LCS round was still a best-of-five. The Reds forced a Game 5 with Pete Rose’s tie-breaking homer in the 12th inning of Game 4. But in the finale, a gem from Tom Seaver (two runs over 8 1/3 innings) punched the Mets’ ticket in a 7-2 win. Alas, the magic ran out in the World Series, where the A’s were victorious in seven games.

6) 2023 NLDS: D-backs (.519) defeat Dodgers (.617) -- 98-point difference
It wasn't just its record that made Arizona the clear underdog in this series. Dodger Stadium itself was something of an antagonist for the D-backs, who had posted a 7-31 record visiting Los Angeles since the start of the 2019 season, suggesting that playing the first two games of a best-of-five series there might spell doom for the upstart club. Not so. Game 1 starter Clayton Kershaw lasted only a third of an inning on his home turf, hammered for six runs in the blink of an eye in what would be an 11-2 loss. The Dodgers' fate was sealed, ultimately, with a historic home run barrage in Game 3, in which the D-backs became the first club to hit four home runs in an inning in postseason play. The clean sweep that sent Arizona to its first NLCS since 2007 would also make, for Los Angeles, the second straight year in which it was eliminated by the club that had finished a distant second in the NL West.

7) 1954 World Series: Giants (.630) defeat Indians (.721) -- 91-point difference
The ’54 Tribe’s winning percentage is still the best ever for an AL team. But despite having two Hall of Famers (Bob Feller and Bob Lemon) in a great rotation and another (Larry Doby) in the outfield, Cleveland had no answers against the Giants in a four-game sweep. It’s remembered most for Willie Mays’ iconic back-to-the-field catch -- better known as “The Catch” -- of a would-be extra-base hit by Vic Wertz in Game 1 at the Polo Grounds. Mays’ subsequent throw to the infield (which was as important as the catch itself) prevented runners from advancing in a 2-2 game, and the Giants won the opener, 5-2, in extra innings. The Indians never recovered.

8) (tie) 2019 World Series: Nationals (.574) defeat Astros (.660) -- 86-point difference
The Nationals had started out 19-31 in the regular season, then went on a run for the ages that included comebacks in the one-and-done Wild Card Game and in the Game 5 NLDS clincher against the Dodgers. They were up 2-0 in this Series, only to drop all three games at home, only to win Games 6 and 7 in Houston, thereby capping the first World Series in history in which the road team won every game. Howie Kendrick’s game-changing homer off the foul pole in Game 7 sent the Nationals to their franchise-first championship and Washington's first since the 1924 Senators.

8) (tie) 2022 NLDS: Phillies (.537) defeat Braves (.623) -- 86-point difference
The Phillies, who had entered the season with the NL’s longest playoff drought (11 years), dismissed manager Joe Girardi after a 22-29 start and turned the reins over to Rob Thomson. They proceeded to go 65-46 the remainder of the regular season, even with reigning NL MVP Bryce Harper on the shelf for two months with a broken left thumb. The Phils entered the postseason as underdogs against the NL Central champion Cardinals in the Wild Card Series but swept them in two games. They were even bigger underdogs against the rested Braves in the NLDS, but took down the defending World Series champs in four games.

8) (tie) 2023 NLDS: Phillies (.556) defeat Braves (.642) -- 86-point difference
Haven't we seen this one before? In an incredibly eerie parallel to the 2022 season, the Phillies again finished exactly 14 games behind the Braves in the regular season, and the Phillies again eliminated the favored Braves in the NLDS. And the similarities don't end there. In each season, the Phillies took Game 1 on the road behind a strong Ranger Suárez start, fell in Game 2 despite having ace Zack Wheeler on the mound to even the series, then used a great Aaron Nola showing in Game 3 to kick-start a two-game stretch of wins in front of the sport's best home-field advantage to clinch the series. The Phillies became the first team in MLB history to beat the same opponent in multiple playoff series when they had at least 10 fewer regular season wins than that opponent in each instance ... and Philadelphia happened to do it in two consecutive years.