For about, oh, 100 or so years, the Cardinals-Cubs rivalry had a rather clear, distinct arc to it. The Cardinals had the titles, the Cubs had the immortal ballpark and the hearts of casual fans everywhere, and the teams had a rivalry that was essentially the friendly Midwestern equivalent of Red Sox-Yankees: true antipathy, but an affable antipathy, as opposed to, you know, this.

I grew up in Central Illinois, where Cardinals fans (like me) and Cubs fans mingled daily, even started families together, in opposition to the partisan, segmented world we live in now. As I put it in 2015, "Your fandom is like disagreeing with a family member about politics; you know they're wrong but you love them anyway. You just hope it doesn't come up at Thanksgiving dinner."

Well, like politics, it's not so easy to be dispassionate and reasonable about the Cardinals-Cubs rivalry anymore. No longer are the Cards the big brother with all the championships, knowing that everyone's rooting for the little brother Cubs but not willing to let them out of the headlock anyway. Essentially since October 2015, the Cubs have eaten the Cardinals' lunch. That October, St. Louis and Chicago, after years of avoiding each other -- they had never once met in the postseason, and had rarely even had pennant chases -- at last faced off in the playoffs, and after the Cards (who had won 100 games during the season) took a 1-0 National League Division Series lead, the Cubs bum-rushed them, culminating in a Kyle Schwarber home run so mammoth and all-encompassing that I'm still hiding under my desk thinking about it.

Last year, the Cubs officially dusted the Cardinals, winning 103 games (while St. Louis missed the playoffs), and then, as you might remember, going on to win their first World Series since 1908. Now, not only are the Cubs the Cards' superior, they're everyone's: The Cubs are the establishment, the team everyone is shooting for. The Cardinals are just another team now, albeit a team that most of America still hates.

It has left many of us Cardinals fans adrift: If we no longer hold dominion over the Cubs -- if every dream of our rival has finally come true, in large part at our expense -- what do we do know? I tried to address this in a piece I wrote shortly after the World Series, saying, "This should be a wakeup call for the Cards and their fans, that they can be no complacency, that now the Cardinals must be innovative and vigilant." But I'm not sure I believed it. The Cubs looked like a far better franchise in the present and likely far into the future. The Cardinals made some nice moves in the offseason, most notably swiping Dexter Fowler from those champion Cubs the same way they'd swiped Jason Heyward the year before (with a ton of money), but not even the most optimistic Cards fan (that would again be me, I think) could argue that they were anywhere close to the Cubs.

Which brings us to now. It's only May 12, obviously, and there is so much time left in the season that no one's going to remember any particular series in two weeks, let alone by the end of the season. But still: This new era of Cubs dominance will put an extra charge into any Cardinals-Cubs series … and this weekend's feels particularly noteworthy. Because -- in a switch from what anyone thought coming into the season, and even thought three weeks ago -- it's the Cards who are in first place, and the Cubs who are reeling.

Now, "reeling" is a relative term here, of course: The Cubs are at .500, which is the sort of reeling the Giants, Blue Jays and Rangers would love to have going on right now. But Chicago is in fourth place in the NL Central, which is pretty astounding, when you think about it: It required quite the leap of imagination to think of one team ahead of the Cubs in the division at this point, let alone three. Much has been made of the Cubs' rotation issues so far -- most notably that they have the slowest-throwing starting pitchers in all of baseball -- but all told, the rotation hasn't been that bad, and you have to think they'll get it figured out or go trade for somebody who can.

The bigger surprise has been the Cubs' supposedly overwhelming lineup. This was supposed to be the Terrordome lineup, the Golden State Warriors' Death lineup, but when you take a look at the numbers, it's a little stunning how many of Chicago's hitters are off to rough starts. Anthony Rizzo is hitting .218; Addison Russell .227; Kyle Schwarber .195; Ben Zobrist .222. Batting average isn't everything, particularly with a patient lineup like the Cubs', but even if you look at OPS+, Rizzo, Russell, Schwarber, Zobrist, Heyward and Willson Contreras are all under 100, which is average. Their best hitters have been Kris Bryant, the Jon Jay/Albert Almora center-field combo and Javier Baez. Everyone else has been worse than average

Obviously -- obviously! -- this can't last. When Schwarber and Rizzo, in particular, get going, this lineup is going to be terrifying again. The Cubs are going to be above .500, far above .500, very soon. They might be there as soon as this weekend.

Which brings us to the Cardinals. Three weeks ago, St. Louis was 3-9 after a humiliating sweep at Yankee Stadium. The team couldn't play defense, it couldn't run the bases and it couldn't hit. (And Matt Adams was running around left field for some reason.) It felt like the Cards were teetering on the edge; was this team going to be a seller at the Deadline? The Cardinals?

Since then, the Cardinals have gone 16-5, the best record in baseball, and they come into the Cubs series having won six in a row, all on the road. And they appear to have found themselves along the way. The strangest part about this is that six-game win streak started the day after outfielders Dexter Fowler and Stephen Piscotty -- inarguably two key cogs for St. Louis' success -- both went down with injuries in the same game. (Piscotty is still on the DL, and Fowler has pinch hit a few times but has yet to start.) What happened? The Cards became the defense and speed-oriented team they kept promising they were going to become. Kolten Wong has been allowed to play second base every day and has (finally) blossomed, and Fowler's and Piscotty's replacements, outfielders Tommy Pham and Magneuris Sierra, have electrified the team. Pham is hitting .417 with three homers -- he has a 1.434 OPS -- and Sierra, who was with Class A Palm Beach a week ago, has come to the plate 19 times and scored seven times. The whole team looks different, a live wire with too much current running through it. It is as exciting as the Cardinals have been since September 2015.

Oh, and don't forget Jedd Gyorko, who has quietly become one of the best hitters in baseball.

But the key, as it always is for the Cardinals, has been the rotation, and it has been the pitchers you didn't expect to be great who have led the way. Lance Lynn, less than 12 months removed from Tommy John surgery, has a 2.75 ERA and is averaging nearly a strikeout an inning; Michael Wacha has a higher ERA but is striking out even more batters. (Wacha is skipping his start against the Cubs this weekend.) But the real star has been Mike Leake, who has a 1.79 ERA in six starts with a WHIP under 1.00. Carlos Martinez, the ace of the staff, is starting to reassert his place atop the rotation, and even Adam Wainwright, who struggled so much early it was difficult to watch him, has started to round himself into at least an average pitcher, with the chance for more. The Cards historically succeed when they have a top-tier rotation and don't when they don't. That has driven this 16-5 run far more than Pham, Sierra or Gyorko.

This has given the Cardinals a 2 1/2-game lead on the Cubs heading into Busch, and on Friday, they face a Triple-A pitcher in Eddie Butler, with Leake, their current ace. This is the first time in the new era of the Cubs-Cardinals rivalry, the world in which Chicago has a World Series championship (it still seems amazing to say that!) and St. Louis is trying to catch up, that the Cardinals have the upper hand. A sweep from the Cubs would eliminate that right quick, and it would reassert their dominance. But the Cards would love to get as much breathing room between them and the Cubs as they can, before the Cubs wake up and take off.

The Cardinals are hotter than they've been in more than a year right now; the Cubs are struggling more than they have since mid-2014. It's the perfect time for them to meet. This rivalry feels much less friendly and affable today. Which is to say: It seems more heated than it has ever been. I can't wait.

* * *
Subscribe to Will's weekly newsletter and email him at leitch@sportsonearth.com.