AL still the much stronger league, but Cubs' success might change that

Joe Maddon managed an overachieving Rays team that had to take chances to catch the Yankees and Red Sox in the AL East. His Cubs are now on the opposite end of that spectrum in the National League. Rob Foldy/Getty Images

In early September, I tweeted something like, "The American League is still the better league." Some fans -- presumably National League fans -- got quite worked up about this, ignoring the facts at hand and creating excuses for the NL's weak results in interleague play. After finishing with a 165-135 advantage in 2016, the AL has now won interleague play for 13 consecutive seasons and owns a 1,897-1,571 advantage since 2004. The AL has played at an 88-win clip over 162 games against the NL during this streak of preeminence.

A few weeks ago, Bill James wrote an article about the strength of the leagues throughout history. "OK, I know that some people don’t want to hear it; I know that some researchers are in denial about it. But the American League has become a significantly stronger league than the National League," James wrote. "It shows everywhere, except maybe the World Series is even. The American League wins interleague play every year, dominates the All-Star game, and National League players moving into the American League show the effects."

There's a reason this might soon end. First, however, it is fun to examine the excuses readers used rather than admitting to the AL's dominance.

The designated hitter. One reader proposed that David Ortiz alone explained the AL's advantage. No, Ortiz does not explain a 326-win edge, especially considering only half of interleague games include the DH. AL DHs have hit better than NL DHs -- since 2009, they have a .336 wOBA compared to the NL's .311 mark -- but that is mostly offset by NL pitchers' hitting better than AL pitchers. Since 2009, AL pitchers have a .118 wOBA in interleague play, while NL pitchers own a .164 mark.

Another way to show this are these results:

NL teams at home vs. AL teams: .503

NL teams at home vs. NL teams: .539

AL teams at home vs. NL teams: .580

AL teams at home vs. AL teams: .536

AL teams improve 44 percentage points at home against the NL, while NL teams decrease by 36 points at home against AL teams. If you want to attribute the .008 difference to the DH, that accounts for about 14 of those 326 wins. The DH advantage is minimal.

A few bad teams drag down the NL's percentage. That seemed like the case in 2016, when the Reds and Diamondbacks went 5-15 in interleague and the Padres went 6-14. Of course, we are talking about league depth here, so every team counts. Even if we ignore the bad NL teams, however, the best AL teams still do much better than the best NL teams. The five NL playoff teams went a combined 57-43 in interleague play in 2016, but AL playoff teams went 67-33. I went back to 2010 and tabulated the interleague records of all the playoff teams:

AL: 396-238 (.624)

NL: 326-281 (.537)

That's a huge disparity. It's equal to 14 wins over 162 games.

Here's another note. The St. Louis Cardinals have been the NL's best team since 2004, finishing better than .500 all but one season and making the playoffs nine times. Look at their splits since 2004:

Against AL: 110-102 (.519)

Against NL: 1070-823 (.565)

That record is even more damning when you realize the Cardinals have played 63 of their 212 interleague games since 2004 against the Royals, who were mostly awful. The Cardinals, in fact, are under .500 in interleague play since going 11-1 in 2004.

The Yankees and the Red Sox. This theory goes that because these two clubs spend so much money, they skew the results. Sure, they have spent a lot on their payrolls. But take them out of the equation, and the AL is still plus-222 wins since 2004. The AL has simply been better and deeper from the top of the league to the bottom.

How did this happen? The simplest explanation involves the Yankees and Red Sox. As those two teams battled for AL East supremacy in the early 2000s and built great teams year after year, it raised the bar for the rest of the American League.

In a follow-up post to his article, James explained this:

      "The Yankees in the late '90s pulled out ahead of everybody, and then John Henry bought the Red Sox and determined not to let the Yankees get ahead of us and just run; we're going to catch them, and we're going to beat them. The rest of the league had to decide: Are we going to let those guys run away with it, or are we going to work harder, take more risks and try to catch them? ..."

When you get one or two strong organizations in a league, it pushes the rest of the league to get better, to work harder. It pushes them to dump that third baseman with the .670 OPS who then goes to play in the NL West and try somebody else.

That's basically it, though there are other reasons. The AL had more teams, such as the A’s, Rays and Indians, ahead of the curve in the sabermetric revolution, but a reason they were ahead was they had to think outside the box to try to catch the Red Sox and Yankees. They had to get smarter. It didn't help that some of the NL's deep-pocketed teams, such as the Mets, Cubs and Dodgers, were behind that curve with their previous front offices (or owners) and thus didn't dominate to the extent of the AL East powers.

In the end, the AL is the stronger league. But the Yankees/Red Sox scenario now has a chance to play out in the NL. The Chicago Cubs were so dominant in 2016 that the rest of the league must now push harder to compete, particularly because the Cubs have the youth and financial resources to continue their success for the foreseeable future.

The Dodgers can't be content winning the NL West with 92 wins and then having to pitch Clayton Kershaw on short rest in the playoffs every year. The Nationals can win the NL East with Ryan Zimmerman playing first base and hitting .214, but they need to aim higher. The Cardinals know 88 or 90 wins won't win the NL Central anymore. As the NL teams currently in a rebuilding cycle get ready to compete, they can't be content aiming for 85 wins and hoping for 90.

That's part of what makes this offseason so intriguing. Even though there aren't many star free agents out there, it will be interesting to see where Yoenis Cespedes, Dexter Fowler, Rich Hill, Aroldis Chapman and Kenley Jansen land. Do the Giants sign a closer or Cespedes? The Cardinals were criticized for signing Brett Cecil to a big contract, but maybe that's the type of risk needed to catch the Cubs.

The NL seems to have as many young stars as the AL -- and maybe more. Front-office turnover in places such as Philadelphia, Milwaukee and Arizona has brought in a new generation of thinking for some clubs. The NL played just .450 ball against the AL in 2016 -- basically the percentage it has played since 2004. I wouldn't expect the NL to beat the AL just yet, but I think we'll start to see the gap shrink.

Or maybe the Cubs will simply win the next five NL pennants.