The 2021 MLB regular season came down to its final day with a lot of potential for chaos — including a possible four-way tie for the American League’s two wild-card slots and contingency plans for multiple extra games just to get the playoff field set. But while Sunday provided some momentary intrigue, the most dramatic of scenarios never quite materialized, as the San Francisco Giants sealed up the NL West and the Boston Red Sox and New York Yankees both claimed the AL’s wild cards. Now we look ahead to the postseason, where a field full of strong teams and plenty of compelling matchups has us thinking that baseball’s October spectacle is just getting started.
How we’re forecasting the 2021 MLB playoffs
Chances of reaching each playoff round for 2021 MLB postseason teams, according to the FiveThirtyEight model
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In the American League, our favorite to make the World Series (at 36 percent) is the defending pennant-winning Rays, who will start the playoffs by taking on the winner of the Yankees-Red Sox play-in contest — two division rivals that Tampa Bay went a combined 22-16 against during the regular season. The Rays will be relying on the familiar formula of a deceptively good offense, a steady defense and a great bullpen to return to the Fall Classic.
But we give the rest of the AL field a 64 percent chance of unseating them, led by the Astros at 27 percent. Houston still has plenty of stars and topped the majors in scoring, though the team is also far from guaranteed to win its division series matchup against a talented White Sox club that features a deadly lineup and strong pitching. And the Boston-New York winner could even make some noise. Though the Yankees have had their ups and downs (and ups and downs, and …) this year, we give the team a very solid 21 percent chance to make the World Series — and an 8 percent chance to win it all — conditional on making it out of the wild-card game. For the Red Sox, those numbers are somewhat lower — 15 percent and 4 percent, respectively — but Boston does have a deep lineup that could make trouble for opposing pitchers. (We give the Yankees a slim 53 percent edge in the wild-card game itself.) It all adds up to an AL postseason bracket where just about anything can happen.
Over in the National League, the Dodgers are also favorites, but that’s mainly a testament to how much talent they have — and not the situation they immediately find themselves in. Los Angeles has that NL-best chance of making the World Series (35 percent) despite having to play a do-or-die game against the Cardinals, MLB’s hottest team since mid-September. Because of this, our model says there’s a 30 percent chance that this Dodgers season — 106 wins and all — ends after just one postseason game. However, if L.A. does beat St. Louis, the Dodgers would immediately become sizable NL favorites, with a conditional 50 percent probability of making the World Series (and a 36 percent chance to win the title).
The Giants are the NL’s second-most-likely pennant winner, and they more than held their own (10-9 head-to-head record) against the Dodgers during the regular season, outdueling them for the NL West crown down the stretch. San Francisco’s franchise-record 107 wins came from scary balance on both sides of the ball. But still, the Giants’ lives would be made much easier if the Cardinals took care of L.A. for them; they would have a 35 percent chance to make the World Series if they faced St. Louis in the NLDS, versus a 19 percent chance if they faced Los Angeles. We can’t overlook the Braves and Brewers, either. In the closest projected division series matchup of them all, we’ll get to watch Milwaukee’s dominant pitching staff go against Atlanta’s powerful lineup. But the NL’s biggest story is how its most talented team on paper will either flame out in a single game or become dominant favorites overnight.
The most likely 2021 World Series matchups
Odds of each matchup of AL vs. NL teams in the 2021 World Series, according to the FiveThirtyEight model
As things currently stand, the model gives a nearly 13 percent chance to a Dodgers-Rays rematch from 2020 — the single most likely World Series matchup in our simulations. However, that means there’s an over 87 percent chance we get a different battle by the end of October. The second-most-likely matchup, at just under 10 percent, is a repeat of 2017 — Dodgers versus Astros — and let’s just say there would be a lot of baggage associated with that one. Third-most likely? At just under 9 percent, Giants versus Rays — a matchup we’ve seldom seen at all (it’s only happened in 15 total games ever, all obviously coming in the regular season). Call it the Evan Longoria Bowl, if it happens. And at just under 7 percent apiece, the next three most likely World Series are Rays-Braves (the Battle of Fred McGriff), Dodgers-White Sox (a rematch of the 1959 World Series) and Giants-Astros (a matchup of former division rivals who now occupy different leagues).1
The 19 other possible permutations come in at varying degrees of lower probability, right down to the least-likely matchup of all: Red Sox versus Cardinals (0.4 percent), itself a rematch of the 2013, 2004, 1967 and 1946 World Series. The odds are stacked against seeing that rivalry be reprised in three weeks’ time — but given how wide-open this postseason field looks, we can’t rule it out entirely.
Check out our latest MLB predictions.