There’s no such thing as a sure thing in baseball. No matter how stacked the favorites are, there will always be teams who will exceed expectations and challenge these big dogs in the playoffs.

Just take for example the Tampa Bay Rays a season ago, who made it all the way to the World Series despite a relatively minuscule payroll.

Let’s take a closer look at the sleepers for the 2021 MLB season’s AL pennant race below. Then, check out all the latest MLB futures odds and lines to start placing stakes on all the exciting baseball betting action as early as this offseason.

READ: 2021 MLB American League Pennant Sleeper Betting Picks

Who Are the Top Sleepers to Win the 2021 MLB American League Pennant?

A nice mix of recent NLCS-winning ballclubs and rising contenders fill out our list of the three best sleeper candidates to win the National League pennant this season. Two of those three teams hail from the NL East, where the race for division supremacy has been hotly-contested for the past couple of seasons.

Boston Red Sox

• 2021 MLB National League Pennant Odds: +2800

There’s no way to sugarcoat the bitter taste that was the 2020 Boston Red Sox season. The boys from Fenway saw their best player in Mookie Betts leave for sunny LA and their top ace in Chris Sale needing Tommy John surgery.

Although the Red Sox’s overall depth is holding them back from being considered as a likely playoff contender this season, the heart of their batting order is still mighty impressive. Sale’s return from injury sooner than expected could give the team a nice boost mid-season as well, leaving plenty of chances for Boston to redeem itself.

Seattle Mariners

• 2021 MLB National League Pennant Odds: +4000

While the Mariners aren’t shy to admit that they are still in rebuild mode for the third-straight year, there are plenty of players that could come as a nice surprise out of this young bunch from the Pacific Northwest.

Veteran leadership will come from Kyle Seager, who’s in the final year of his contract in Seattle and could break loose in order to boost his value in next season’s free agency market. 21-year-old outfielder Jarred Kelenic is also expected to make his major league debut after dazzling Mariners scouts and coaches in the minors.

With a promising young core of talent at their disposal, the M’s are indeed among the 2021 MLB AL pennant sleepers this season should their budding prospects all pan out simultaneously.

Kansas City Royals

• 2021 MLB National League Pennant Odds: +5000

The Royals are in an unenviable position of being pitted up against a very crowded AL Central scene, with the Twins, White Sox, and Indians each having better claims to the division title than KC as we speak, based on MLB betting odds.

Still, the Royals made a few nice moves during the offseason to increase their chances of capturing the American League pennant for the first time since winning the World Series in 2015. In particular, the signing of Silver Slugger Carlos Santana, who’s haunted Kansas City’s bullpen in prior seasons, is a nice boost to the team’s batting order.

Throw in a lefty-dominant starting rotation with southpaws Danny Duffy, Mike Minor, and Kris Bubic into the mix, and the Royals have all the makings to be an unorthodox sleeper candidate to win the AL when all is said and done.

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*All stated odds are subject to change without prior notice.