The 2021 MLB playoffs are nearly at hand, and if the end of the regular season is any indication, the postseason is sure to give us a mad month full of unpredictable baseball. Right now, our MLB forecast model assigns eight teams at least a 5 percent chance of winning the World Series, and each team comes with its own storylines — and problems that must be solved if it is to win the championship. Here are the biggest questions facing each of the most likely contenders in the postseason field:

Los Angeles Dodgers

World Series probability: 24 percent
Burning question: Can they avoid the pitfalls of past repeat bids?

Ever since the New York Yankees won their third consecutive World Series in 2000, 20 MLB champions have attempted to repeat as winners the following season. All 20 failed. The Dodgers are hoping to break that streak, and they certainly have the talent to do it: L.A. is the best team in baseball according to a variety of different measures, tracking for the 11th-highest final regular-season Elo rating of any NL or AL team since 1901. Despite getting less production than expected from their biggest stars, the Dodgers are also closing out the regular season with the most wins above replacement of any team through games of Sept. 29, including MLB’s No. 1 starting rotation, No. 4 bullpen and No. 6 position-player corps. But plenty can derail even the most talent-laden team in the postseason, not least of which is the prospect of facing the red-hot St. Louis Cardinals in a do-or-die wild-card game (if the archrival San Francisco Giants hold on to take the NL West crown). And even if they make it through the single-elimination gauntlet, this L.A. lineup is not quite as dominant as it was during last year’s World Series run. So while the Dodgers may have built an impressive baseball machine, that can’t necessarily save them from the same fate that befell those other 20 defending champs before them.

Tampa Bay Rays 

World Series probability: 17 percent
Burning question: How much does their shaky starting rotation matter?

Following up on their trip to the World Series a season ago, the Rays might be even better in 2021. They have a superior Pythagorean winning percentage this year to go with a better regular-season Elo rating. (In fact, the team set a new franchise high-water mark for Elo at the end of August.) Relative to the league, this team ranks higher in WAR from its batting, baserunning and relief pitching while still maintaining an elite defense. The only area in which last year’s Rays were clearly better is in starting pitching, where Tampa Bay has fallen from 12th to 19th in rotation WAR after the team said goodbye to Blake Snell and Charlie Morton and then Tyler Glasnow injured his elbow in mid-June. The leftover starters have featured a few good contributors — such as hard-throwing lefty Shane McClanahan, ex-Brewers righty Drew Rasmussen and (most recently) 22-year-old prospect Shane Baz — but mostly it’s a middling group that has struggled to eat up innings. But entering the playoffs, when relief pitching has mattered a lot more in recent years, the Rays’ biggest liability might not be too much of a concern, and perhaps the team that helped pioneer “bullpenning” can ride the game’s best pen to a title. And it’s worth remembering that, even in last year’s World Series run, the starting trio of Snell, Glasnow and Morton accounted for 45 percent of Tampa Bay’s total postseason innings.

San Francisco Giants 

World Series probability: 12 percent
Burning question: Can the magic of 2021 extend through the postseason?

Raise your hand if you had San Francisco winning 105 games this season back in spring training. (OK, stop lying!) This Giants team has truly had one of the greatest out-of-nowhere campaigns in baseball history. Among AL or NL teams that won at least 105 times (per 162 games) in a season, only two — the 1918 Cubs and 1946 Red Sox — had fewer wins per 162 in the previous season. That these Giants did it as MLB’s oldest team (average age: 30.3) has made the performance even more remarkable. The biggest question left for San Francisco now is whether it can finish the job in the postseason the way teams from its previous dynasty did. Make no mistake: This team is no mere fluke. The Giants have MLB’s second-best Pythagorean record, second-best Base Runs predicted record and second-most WAR. They also have one of the most well-rounded rosters in baseball, ranking among the top five in WAR from position players, starting pitchers and relievers. However, it takes a large sample of games to change our priors in baseball, and Elo still doesn’t place San Francisco on the same level as the Dodgers and Rays at the top of the power rankings (despite the Giants beating L.A. for the NL West title). Maybe that’s just the algorithm’s way of doubting whether Kevin Gausman, Anthony DeSclafani, Brandon Crawford and Buster Posey are really as good as they’ve seemed in 2021 so far. But for a team without many other glaring concerns on paper — save for perhaps Brandon Belt’s late-season thumb injury — all we might have to ponder is how durable the Giants’ breakout can be in October.

Houston Astros 

World Series probability: 12 percent
Burning question: How far can their lineup carry them?

After a down regular season in 2020, the Astros have bounced back with a vengeance this year, leading all clubs in weighted runs created plus (wRC+) and batting WAR, and ranking second in runs per game. The team’s core group of Carlos Correa, José Altuve, Yuli Gurriel, Yordan Álvarez, Kyle Tucker and Michael Brantley all ranked among MLB’s top 50 hitters by wRC+, and Alex Bregman would have tied for 47th if he had qualified. Although Brantley has been dealing with a recent knee injury, the rest are healthy, and they collectively give Houston a lineup that no opponent wants to face over and over during a series. At the same time, however, the Astros have a flawed pitching staff with a mediocre bullpen (No. 18 in relief WAR and No. 25 in win probability added) and a rotation that is short on previous postseason experience — particularly since Zack Greinke’s neck injury will likely limit him to relief duty. Houston still ranked sixth in ERA (aided by MLB’s fourth-best defense by WAR) and 12th in fielding independent pitching, so this staff is by no means a total liability. But the Astros go into the playoffs as an offense-first ballclub with more question marks on the mound than they had when they went to the World Series with the No. 1 pitching staff by WAR back in 2019.

Milwaukee Brewers 

World Series probability: 9 percent
Burning question: Can this offense put enough runs on the board?

With a 66-39 record (third-best in MLB) since June 1, Milwaukee overcame an up-and-down start to command a place among baseball’s best teams for the majority of the regular season. The Brew Crew also come into October armed with a number of factors that usually portend postseason success (as much as anything really does): a dominant rotation headlined by Corbin Burnes, Brandon Woodruff and Freddy Peralta; a strong bullpen that saved its best performances for the biggest moments; and the fifth-best defense in the league by WAR. The only nagging issue around this team all season has been its offense, which ranks just 22nd in wRC+ and 23rd in batting WAR, with lineup mainstays Christian Yelich (100 wRC+), Lorenzo Cain (100) and Jackie Bradley Jr. (37) all delivering unremarkable performances at the plate. Milwaukee’s hitting problems seemed to improve after the midseason acquisition of Willy Adames, and the Brewers’ OPS was actually 7 percent better than average in June, July and August. But with Adames in and out of the lineup because of an injured quad, Milwaukee’s OPS is back to 10 percent worse than average in September, reviving concerns about whether a lack of hitting will derail a team that otherwise has all the attributes of a World Series squad.

Chicago White Sox 

World Series probability: 8 percent
Burning question: Have they just been unlucky in tight games?

Hardly a one-hit wonder from the pandemic-shortened 2020 campaign, the White Sox are having another fine season in 2021 despite myriad injuries. They clinched the AL Central last week and are on track for 93 wins, which would be the most for the franchise since it won the World Series in 2005. The Pale Hose have plenty of strengths (a killer lineup, a deep pitching staff) and, yes, a few weaknesses (bad defense, poor baserunning) that will probably factor into how long their postseason trip lasts. But one of the more interesting side notes about the White Sox is that they are 74-44 — fourth-best in MLB — in games decided by multiple runs, but just 17-24 — fourth-worst — in games decided by a single score, giving them the worst record in one-run games among playoff contenders. What does it mean? Normally you might blame a shaky bullpen for such a split, but Chicago’s pen has the fifth-most relief WAR of any team (though they do perform worse than expected in high-leverage situations). It could also be an artifact of the offense performing worse in clutch moments, too. Either way, the conventional sabermetric wisdom is that such differences in the clutch are mostly noise — or at least not meaningful enough to override great overall numbers like the White Sox have. And if it was simply a matter of bad luck, we wouldn’t expect the White Sox to carry their regular-season struggles in close games over into the playoffs. But we’ll see.

Atlanta Braves 

World Series probability: 8 percent
Burning question: Can they keep the late-season momentum going?

Like several other eventual playoff teams (hello, Cardinals), the Braves’ postseason chances were looking less-than-inspiring during the heat of the summer. For instance, on July 29, a day before the trade deadline, Atlanta had just a 20 percent chance to make the playoffs. But from July 30 onward, the Braves have a 35-19 record (sixth-best in baseball), and they clinched their fourth straight NL East title by overtaking the flagging Mets and holding off the stubborn Phillies. The key ingredients have included good hitting from in-season acquisitions Jorge Soler, Adam Duvall and Eddie Rosario, but also much-improved pitching. Through July, Braves hurlers were allowing an OPS of almost exactly the league average; ever since, their OPS allowed is nearly 20 percent lower than average. With most of their best pitchers healthy and playing well down the stretch, the Braves enter the playoffs in better shape on the mound than they did last year, when they came within a game of making the World Series despite a patchwork staff. And in turn, that could have Atlanta peaking at exactly the right time.

New York Yankees 

World Series probability: 5 percent
Burning question: Which Yankee team will show up in October?

Tabbed as our model’s second-most-likely World Series winner in spring training, the Yankees have sometimes looked the part … and sometimes, uh, not. Since the start of July, New York has had a stretch with 35 wins in 48 games (including a 13-game winning streak in late August), followed by three wins in its next 15 games, and then this current 12-4 stretch to help propel it to the brink of the playoffs. So which version might we get in the postseason? Reasons why we could see the Good Yankees include the team’s strong bullpen (No. 9 in win probability added and No. 2 in relief WAR) and a resurgent lineup that has strung together two straight above-average OPS months for the first time all season. But the Bad Yankees could just as easily appear. At its core, this remains a team that doesn’t add runs on the basepaths, gives too many away on defense and — with a run differential of just +52 — is probably lucky to be in playoff position at all. Despite that, though, the Yankees are still hoping this roller coaster of a year has another rise left in it.

Check out our latest MLB predictions.