There are eight teams left in the postseason tournament, and four of them – the Dodgers and Braves in the NL, and the Orioles and Astros in the AL – have yet to appear in a game, having locked up the top two seeds in each league and the first-round bye that goes along with it.

They’re here in the Division Series because they’re the best, with three of the four clubs winning 100 games or more, and the fourth, Houston, falling well short of that mark yet still with a run of six consecutive full-season division titles alive and well.

But it’s a long season, and things can and do change; look no further than the fact that only one member of the Dodgers' five-man Opening Day rotation (Clayton Kershaw) is still here. Justin Verlander started the year in New York, and Grayson Rodriguez spent a big chunk of his summer at Triple-A Norfolk. Remember Félix Bautista? Exactly. Things aren’t necessarily what they were.

What you thought you knew about these teams in April or even July might not reflect what’s actually true about them today, in October. Here’s what to know about The Big Four – and how it may not be what you expected.

Orioles

What you may think they have: A thin rotation and a dominant bullpen

What they actually have: Maybe the exact opposite of that?

That the 2023 Orioles overperformed every reasonable expectation is largely due to the fact that entering the season, no one considered their rotation to be terribly strong. (Well, that, and that absolutely no one could have expected unexpected names such as Yennier Cano, Aaron Hicks, Danny Coloumbe, and Ryan O’Hearn to contribute over 7 Wins Above Replacement just from the four of them.)

Entering the season, the O’s rotation was projected to be the 28th-best, and if that sounds harsh, realize that through the first half of the season, they were indeed all of 25th-best – score one for the projections. Meanwhile, while their bullpen was projected to be just OK (21st), it actually became baseball’s best first-half bullpen, largely, again, because of the unexpected emergences of Cano and Coulombe ahead of 2022 breakout star Bautista.

… and then what happened?

What happened is that the rotation got filthy. Rookie Rodriguez posted a 7.35 ERA in 10 early-season starts, got demoted for two months, and has been one of the best starters in the game since his return (2.58 ERA in 13 second-half starts). John Means, a 2019 All-Star, returned from injury and allowed just seven runs in four late-season starts. Kyle Bradish, who had a 4.90 ERA last year, became the first O's starter since Mike Mussina in 1992 (2.54) to post an ERA under 3.00, finishing at 2.83. Early-season starters such as Tyler Wells and Cole Irvin are now relievers. The September Orioles starters had the third-best ERA and tied for fourth-most WAR.

But the flip side of that is that the bullpen has really backed up, and while most of that is because of the season-ending arm injury to Bautista, that is not all. Cano entered September with a 1.56 ERA and a 23% strikeout rate; his final month had marks of 5.79 and 18%, respectively. Coulombe’s 2.59 and 30% through August became 3.72 and 17% in the final month. Put it all together, and something quite terrifying happened:

Orioles relievers strikeout rate

• April-August: 26.2%, 4th-best
• September: 20.3%, 4th-worst

Given the realities of the roster, it’s both better than that and worse: The reliever who faced the third-most innings in September was the recently released Jorge López, who was both ineffective (5.25 ERA) and a good strikeout arm (28%) last month. It might mean nothing, that a heavily worked ’pen was running out of gas and that the rest will do them good. Or it might mean that a group much weakened without Bautista really needs the rotation to pitch like the plus unit it now seems to be.

Astros

What you may think they have: A catcher well-equipped to shut down the running game.

What they actually have: A situation that is very much not that.

Their catcher is nicknamed “Machete,” after all, and we don’t think it’s because of Martín Maldonado’s expertise with a sharpened blade. It’s because of the cannon arm that once rated among the elite in baseball in arm strength. Though he’s got more pop in his bat than you’d think (15 homers this year), what keeps Maldonado in the lineup every day – often to the angst of Astros fans, many of whom would much rather see rookie Yainer Diaz’s 23 homers and .846 OPS – is his defense. It would have to be, anyway, because over the last four seasons, Maldonado has hit all of .186/.271/.338.

For years, the defense was good enough to support that. In 2017, for example, Statcast graded Maldonado (then with the Angels) as the second-best defender at any position, and he’s rated well enough since … until this year, when a 36-year-old Maldonado’s metrics fell off so badly that he’s graded as second from the bottom among catchers, though that’s mostly about pitch framing. When he threw out a runner on Sept. 30, it marked the first time he’d done so in two months, since July 31.

In September, then, the Astros allowed 34 steals, the most in the American League, and tied for second-most in the Majors. But there’s something interesting about what’s happening here, too. According to Statcast metrics, which take into account the difficulty of steal situations based on runner speed, lead allowed, and other inputs, both Houston catchers are … perfectly fine at this. Fine to even good.

• Maldonado: +2 steals above avg
• Diaz: +4 steals above avg
• Houston C overall: +5, or 5th-best

How is that possible? Because Houston pitchers simply do not put their catchers in position to succeed. On steal attempts from first, when the ball reaches the plate, runners trying to steal against Houston pitchers are only 54 feet from second – the shortest distance of any team. In a forthcoming Statcast metric that will show the performance of pitchers in preventing stolen bases, Houston’s pitchers will rate second from the bottom, with José Urquidy, Hunter Brown, and Cristian Javier appearing particularly weak.

Astros pitchers – and more importantly, manager Dusty Baker – swear by Maldonado, who is almost certainly going to start most or all of Houston’s postseason games. Maldonado might not be what he once was, but in the running game, these problems start on the mound. It’s up to the Twins to take advantage.

Braves

What you think they have: A fully formed, unstoppable baseball machine.

What they actually have: A pitching staff with a ton of questions.

The Braves won 104 games. They tied the all-time record for home runs with 307, they became the first team to slug over .500 for a full season (.501), and they tied the 1927 Yankees for The Best Offense Ever, so if the absolute worst thing you can say about their lineup is “well, Sean Murphy faded down the stretch a bit” then you know things are going well. Their offense is a fully formed unstoppable baseball killing machine. If Philadelphia pitching can’t find a way to stop Ronald Acuña Jr. and friends, then nothing else might matter.

But even though it’s not really true that “good pitching beats good hitting in the playoffs,” the Braves are going to be an incredibly interesting test of that old chestnut, because in September, their ERA was 5.61, the third-weakest in the Majors. In the second half, their 4.76 ERA was 10th-weakest. It’s true that some of that came from pitchers who won't be on the NLDS roster. It's still not how you want to head into October.

So what happened here?

• Injuries. Charlie Morton hurt his finger in September and is ineligible to return until the NLCS, at the earliest. Kyle Wright, their breakout star of 2022, made five early-season starts before a shoulder injury knocked him out for months; he’s likely to be a reliever in the NLDS. Max Fried, their Opening Day starter, missed time with arm and hamstring injuries, and he’s now trying to heal enough from a blister to start Game 2.
• Performance. While Bryce Elder’s early-season All-Star run was a welcome boost (2.45 ERA in first 17 starts), the underlying metrics didn’t support that, and he then posted a 5.75 ERA in his final 14 starts. It’s unclear if the team views him as a starting option in the NLDS. The normally reliable Raisel Iglesias saw his strikeout rate dip to 20% in September, the lowest in a month of his career. It’s worth noting that in a postseason ruled by velocity, only two bullpens threw fewer pitches at 95-plus mph than Atlanta relievers did – and the Phillies had the most.

If this seems like mere doom-and-gloom – that it’s nitpicking to find flaws in what was unquestionably baseball’s best team – then remember that it was just a year ago that a late-season oblique injury to Spencer Strider and Fried’s battle to overcome illness left the favored Braves with a thinner-than-expected pitching staff headed into the NLDS against these very same Phillies, who beat Atlanta in four games on their way to the World Series.

Atlanta has, understandably, the highest odds of any club to win the World Series. But those odds, currently 27% at FanGraphs, say they won’t do it three-quarters of the time. If that happens, this is going to be why.

Dodgers

What you think they have: A tattered starting rotation

What they actually have: No rotation at all

Sometimes, the eye test is correct. You know that whether due to injuries, trades, or administrative leave, almost all of the Opening Day rotation for the Dodgers is unavailable, and the lone remaining arm, Kershaw, is clearly a diminished version of himself due to ongoing shoulder concerns.

Los Angeles was the only team in baseball this year to not have a single starting pitcher make 25 starts. (Kershaw made 24.) They’re the only team in baseball this year to not have a single starting pitcher throw 135 innings. (Kershaw had 131 2/3.) Since the Majors went to six divisions in 1995, there have been 168 teams to win their division, and 167 of them had at least one starter make 25 starts. Guess which one didn’t?

What they’ve done is pretty unprecedented, is the point, and it extremely remains to be seen if this kind of approach can work in the postseason. Kershaw will start Game 1, but he’s not completed even six innings or thrown 90 pitches since June, or pitched on less than five days rest since May. Rookie Bobby Miller will likely follow in Game 2, a position wildly beyond what anyone might have expected when he missed much of the spring with shoulder trouble.

After that, it’s a grab bag of rookies (Emmet Sheehan, Ryan Pepiot) with no postseason experience, or struggling veteran Lance Lynn, or endless streams of relievers. You might see openers. You might see starters yanked after a single time through the lineup. That there are days off between Games 1 and 2, and if necessary after 4, will allow Dave Roberts some time to rest his most valuable arms.

So, what you might see is a challenge to this ignominious “record” that we just made up. Dating back to 1969, and excluding the 2020 postseason, there have been 180 teams to throw at least 50 innings in a postseason. Only two teams have done it with their starting pitchers throwing less than 40% of postseason innings:

• 35% // 2018 Brewers
• 37% // 1984 Padres

(Wait, 1984? It wasn’t a strategy so much as it was San Diego improbably surviving their starters pitching poorly in the NLCS, and then not surviving their starters pitching poorly in the World Series.)

If you thought there was grumbling about how the Blue Jays just managed their starting pitching in the Wild Card Series, then wait for this one. Dave Roberts is going to have to pull some pretty unpopular rabbits out of his hat this time around.