This time of year excites me for two reasons. One, of course, we’ve got the playoffs coming up, and no matter what you think about how the tournament is designed, this month is as exciting as baseball can get. Today and tomorrow, teams will be eliminated! Everything ends, ever so suddenly! It’s a gas. The other thing I love, though, is that all the season statistics are final. For the first time, I get to stop worrying about projections or extrapolations. What happened has happened. There is no more of the regular season, so the numbers on the leaderboards are as they will be forever.

It makes the writing easier, and more matter-of-fact. For example, here is a matter of certain fact: The 2017 Houston Astros had baseball’s most improved lineup. How can I say that? No one else improved by nearly so much in wRC+.

Last season, the Astros scored 4.47 runs per game. Their non-pitchers batted more than 6,000 times, and they combined for a 101 wRC+ that ranked 15th in baseball. Put them right there with the Rockies. This season, the Astros scored 5.53 runs per game. Their per-game average, in other words, got better by more than a full run. Their non-pitchers batted more than 6,000 times, and they combined for a 122 wRC+ that ranked first in baseball. First by 11 whole points!

What’s the difference between 122 and 101? The answer is 21. That’s how much the Astros improved, with the Yankees managing the second-biggest improvement, at +15 points. The A’s were the only other team with an improvement in the double digits. You’ll probably notice another team stands out — the Red Sox got worse by 22 points. They got that much worse and still they won their division. For future teams, I wouldn’t recommend following the Boston course, but at least they do demonstrate there’s more than one path toward the playoffs.

We can break this down into core components. The plot above shows overall changes in wRC+. In here, we can just focus on team walk rate.

Pretty boring. Not much going on. Only the Dodgers changed by two percentage points. The Giants bring up the rear, getting worse by a point and a half. If you search, you’ll find the Astros, fifth from the right. Although the Astros offense dramatically improved, it did not get better at drawing walks. Perhaps that’s not what you’d expect. Right here is the real turnaround. Here is the same plot again, but now focused on strikeout rate.

The A’s team strikeout rate increased by more than five points. The Rangers team strikeout rate increased by more than four points. The Angels team strikeout rate increased by more than three points. Those are over there to the right. The second-biggest team improvement belongs to the Indians, who reduced their rate by 1.7 points. The Astros reduced theirs by 6.2.

Last season, the Astros had the fourth-highest team strikeout rate in baseball. The other three teams repeated with high strikeout rates this summer. The Astros, meanwhile, wound up with the very lowest strikeout rate, by more than a point. No team hit for more contact than Houston did, which isn’t to say it was entirely unexpected, given that projections indicated something like this would happen all the way back last winter. Still, predictable or not, the Astros offense adopted a new identity. As the rest of the league has grown more accepting of strikeouts at the plate, the Astros have gone the other direction, and now, consider this: the league-average non-pitcher this year struck out 21.2% of the time. Not a single Astros hitter expected to play with some regularity in the playoffs struck out that often. Everyone — everyone — was better than average.

We’ve looked at walks, and we’ve looked at strikeouts. Might as well also look at power.

The A’s hit for more power, but struck out more often. The same goes for the next four teams. Not the Astros, who had the biggest improvement in strikeouts, and the sixth-biggest improvement in power. With a blend like that, you can sacrifice a handful of walks if you have to, because having contact and power is the modern ideal. It’s all enough to make you want to consider the Astros in a historical context.

This year, 48% of all non-pitcher plate appearances went to players who wound up with sub-100 wRC+ marks. The Astros finished at just 17%, many of those plate appearances going to an underachieving Carlos Beltran. But now, let’s look at some things I checked in July. The Astros finished with a non-pitcher team wRC+ of 122. By itself, that’s tied for 13th-best for any team since the turn of the last century. The Astros were also better than the next-best team by 11 points. That moves them up into a tie for ninth-best.

Now for one last analysis, which tries to consider the spread of talent in each season. For every year since, again, 1900, I calculated the standard deviation in team wRC+. I then calculated z-scores, to measure distance from the league average. Here are the top 10.

Best-Hitting Teams Team Season wRC+ Z-Score Reds 1976 130 2.90 Astros 2017 122 2.82 Mets 1987 116 2.56 Pirates 1902 126 2.51 Yankees 2007 120 2.51 Reds 1918 120 2.47 Blue Jays 2015 117 2.42 Athletics 1913 127 2.37 Yankees 2009 118 2.34 Yankees 1931 133 2.33 1900 – 2017, non-pitchers only.

By this measure, this year’s Astros were 2.8 standard deviations better than the average lineup. Only one lineup has been superior, that one belonging to the 1976 Reds, who won 102 games and the World Series. I’ll note that you can achieve some further separation if you take baserunning into account — those Reds could motor, whereas these Astros generally don’t do so much of that. But no one’s trying to make the argument that the Astros have the best lineup ever. They just have one of them, thanks to an improvement in power, and a massive, massive improvement in contact. For several years in a row, the Astros struck out more than just about any other team. This year, they put balls in play, or they put balls beyond where being in play was possible. Two good things to do, when you know you have guys who can swing with authority.

It’s fairly remarkable the Red Sox could decline as much as they did and still win a division. Maybe I shouldn’t have just glossed that right over. But at least for this post, I wanted to focus on the Astros, who have positioned themselves as very much a championship contender. Consensus opinion still holds, that in the playoffs, good pitching beats good hitting. Whether it beats great hitting, though — that’s what the Astros are intending to test.