The 2019 MLB season has been full of captivating storylines and spectacular performances. However, cream rises to the top, and three teams in particular have asserted themselves as the best teams in the league.

Both the Houston Astros and New York Yankees have dominated a top-heavy American League, while the Los Angeles Dodgers have rampaged through a very crowded and somewhat underwhelming National League.

For weeks now, the narrative has been that the Dodgers are practically a shoe-in to represent the NL in the World Series, even after they failed to add an impact bullpen arm at the deadline. In all likelihood, they would be met there by the Astros or the Yankees, two of the more prolific offensive teams in the league that also boast pitching strengths of their own (Houston's three aces and New York's bullpen).

Yet, October baseball is a completely different beast. The pressure heightens significantly, and sometimes an underdog matches up well with their high-powered opponent. Anything can happen… just ask Yankees fans about the 2004 ALCS, or Cleveland Indians fans about the 2016 World Series.

Indeed, there are a number of teams that could pose significant threats to the aforementioned “best teams in baseball” come playoff time.

Here are the teams that could play “spoiler” and pull off a playoff shocker come October

National League

Let's start with a few teams that could defeat the mighty Los Angeles Dodgers, shall we? While the Astros and Yankees might have to face off against one another in the ALCS in order to reach the World Series, there does not seem to be a clear challenger to Los Angeles in the National League.

The Dodgers own the best record in the National League by a whopping nine games, and their +206 run differential is the best in the MLB. They have possibly the best starting rotation in baseball, and a lineup anchored by MVP candidate Cody Bellinger.

However, the Dodgers hardly have the most elite bullpen, and it is unknown whether Kenta Maeda or Rich Hill will end up being the fourth starter in October.

Note: this list will not include teams like the Braves or the Cubs, who might be considered the stiffest competition in the quest for the National League pennant. With that in mind…

Washington Nationals

Yes, Washington's bullpen is far worse than L.A.'s, and they are not nearly as deep. Injuries could very well deplete the roster prior to October. But say they earn a Wild Card berth and win the play-in game to set up a matchup with the Dodgers? That is a scary proposition for Los Angeles.

Washington arguably offers a superior top three in their rotation. Yes, all of Hyun-Jin Ryu, Walker Buehler and Clayton Kershaw have been tremendous for the Dodgers, but I would just as soon take Max Scherzer, Stephen Strasburg and Patrick Corbin. After all, they have a higher cumulative fWAR while also boasting stronger peripherals.

In a five-game series, quality starting pitching is at a real premium. Both Scherzer and Strasburg have shown the ability to dominate and go deep into postseason games, and Corbin is the perfect guy to neutralize Los Angeles' left-handed heavy lineup.

The Nationals have arguably had one of the more disappointing lineups in baseball, ranking just 14th in baseball with a 97 wRC+ (as of Wednesday). However, they are one of the deeper teams in the NL outside of the Dodgers, deploying guys like Howie Kendrick and Gerrardo Parra off the bench.

Washington leads the National League in stolen bases, and their ability to put runners in motion could have a massive impact on the series, especially if the starters (on both sides) perform and every run is suddenly crucial.

This could indeed be a series that comes down to the bullpen. The Dodgers have a clear advantage here, but Washington's starters could do just enough to earn three wins. Los Angeles leads the season series 4-3, but are up just three in run differential. This has been a tight matchup throughout the year.

These two teams went to five games in the NLDS in 2016, and there is no reason that this hypothetical series could not turn into another thriller.

New York Mets

The Mets have a similar argument for beating the Dodgers as the Nationals: premium starting pitching. Their starters lead the MLB in fWAR in the second half, with Jacob deGrom embarking on a ridiculously dominant stretch over the course of the last three months.

Perhaps contrary to popular belief, the Mets have also had an above-average offense this season, and their 102 wRC+ value actually ranks above the Nationals, despite the fact that New York lacks a superstar of the same caliber as Anthony Rendon or Juan Soto.

Amed Rosario has really come around in the second half, and Pete Alonso is having a good start to August after struggling in July. Michael Conforto is one of the more underrated hitters in baseball, and J.D. Davis has been a blessing in the lineup. Not to mention, Jeff McNeil leads the league in batting average.

The Mets also have some depth of their own, and perhaps even more depth than the Nationals when healthy. If guys like Dominic Smith and Brandon Nimmo can come back at full strength and be effective, the Mets are going to have plenty of options in the lineup. Heck, maybe Jed Lowrie even decides he is ready to contribute come October.

Similarly, the Mets might gain confidence from the fact that they beat the Dodgers in the 2015 NLDS en route to their first World Series appearance since 2015.

This is yet another matchup that could be determined by the bullpen, where the Dodgers again have the advantage. However, things may be looking up for the Mets in this regard. Seth Lugo has been dominant since being named the closer, and they have plenty of talent if Edwin Diaz and Jeurys Familia can round into form.

The Mets are one of the hottest teams in baseball. If they can ride this momentum into October, why shouldn't they be the team to take down the Dodgers?

St. Louis Cardinals

By all accounts, the Cardinals should not be on this list. They rank just 23rd in wRC+ (88), and the quality in their starting rotation does not come close to matching that of the Nationals or the Mets.

So, why am I including the Cardinals? They are the only team in the National League that has a winning record against the Dodgers, going 4-3 in seven games against Los Angeles.

Yes, all four wins came via a sweep in April, and yes the Dodgers just recently returned the favor by sweeping the Cardinals last week. Indeed, the Dodgers are a much stronger team than they were in April, but the Cardinals have also gotten off to a good start in the second half.

The Cardinals are 18-11 since the All-Star break, and Jack Flaherty has been absolutely electric. Although he failed to live up to preseason hype in the first three months of the season, Flaherty has a 0.70 ERA and 11.7 K/9 in six second-half starts, reminding teams around the league why he was a popular sleeper pick to win the NL Cy Young Award.

Paul Goldschmidt dominated in July, slashing .308/.360/.725 and clubbing 11 homers, and Kolten Wong is having an excellent second half thus far.

Contrary to the Dodgers, the Cardinals also have a number of bullpen arms that they can use in long relief and late-game situations. Giovanny Gallegos, John Brebbia and John Gant have all been superb, and Andrew Miller still has great stuff, if he can cut into his walk rate.

The Cardinals seem like a long shot because they are not nearly as balanced as other National League contenders, but do not count them out. What if Flaherty steals Game 1 in Los Angeles? What if Goldschmidt gets hot or Matt Carpenter finds himself again? They have the kind of personnel to pull off the upset.