Everyone has their own definition of big fun. High on my list is the four-game series between the Chicago Cubs and Washington Nationals that started Thursday night with a 5-2 victory for the Cubs at Wrigley Field. Every inning of every game will be worth enjoying and analyzing. By Sunday night we might not know where these teams stand relative to each other, but we will sure know a lot more.

For jubilant context, the Cubs and Nats entered their faceoff with the two best records in baseball as well as the best team ERAs, both marks insanely and unsustainably great (2.32 and 2.35) . These clubs also may have the two most cheerful baseball-as-joy managers in the game: Joe Maddon and Dusty Baker. They’re baseball lifers and students of the sport, and both believe that confidence, relaxation and fun are almost as important as talent.

[Joe Maddon on Bryce Harper: ‘He respects the game’]

Maddon once allowed a pet python into his clubhouse. Baker last quoted a Van Morrison lyric one day ago. If Maddon had Bryce Harper and Jayson Werth, he would want them to get more expressive hair styles. Baker co-invented the high-five. Maddon wishes he had. If these clubs tie for best record in the National League, home field in the playoffs should be decided by best managerial air guitar.

Here’s a secret: Under their smiles, both men have managed one World Series team — and lost. Neither is happy about it. Both are on a quest, as much as any manager. They just hide it because they think anxiety is a baseball toxin. Cool and calm is their crusade. That isn’t easy either.

The Chicago Cubs' underground, 30,000-square-foot clubhouse features hyperbaric chambers, a float pod, mood lighting and much more. "This is the most expensive of all the clubhouses that were built in the modern age," said the Cubs business president Crane Kenney. (Jenny Starrs/The Washington Post)

[Fearing no jinxes, Cubs embrace World Series favorite status]

These clubs also will match baseball brains. Cubs General Manager Theo Epstein is a double World Series champion legend and hires many of the best front-office minds in the game. The Nats’ Mike Rizzo isn’t far behind, and with pitching coach Mike Maddux and base-thief guru Davey Lopes joining Baker’s staff, the Nats have elevated their baseball IQ as much as any team.

With far more shifts, the Nats own baseball’s second-best “defensive efficiency” — that means turning batted balls into outs through blatant theft. Who’s better? Only the Cubs.

What we will see this weekend is just the first battle of what may be a long-running war. Since the start of 2011, only one team in MLB has won more games than the Nats (the Cardinals). But last season, the Cubs arrived with 97 wins. The Cubs’ lineup is loaded with precocious kids who are under team contract for years, while the Nats are so soundly, deeply and inexpensively built that this is probably the start of a Cubs-Nats rivalry for, at least, the next three seasons.

The NL team with the most money is still the Dodgers and those with the most regal pedigrees, still intact, reside in St. Louis and San Francisco. But for the next few years, I’ll take the chances of the Cubs, Mets and Nats reaching the World Series; you get the other dozen.

How scorching are the Cubs? No team since 1905 has outscored its first 26 opponents by such a huge margin: 93 runs. If not for that monster margin, the Nats’ run differential of plus-50 would be remarkable.

However, all is not as it seems in measuring these two teams at the weigh-in. “Everyone knows” that the Cubs’ record is legitimate because they have supposedly played a normal schedule while the Nats, we’ve told ourselves, have played patsies. As is often the case, “everyone,” including me, may not be looking at the whole picture. Based on last year’s records and preseason reputations, the Cubs have faced representative foes. And the Nats, until they recently went 5-1 in St. Louis and Kansas City, faced teams with “bum” tags.

Washington Nationals pitchers Max Scherzer has nearly 60 dives under his belt and has traveled to Fiji, Mexico and the Caymans. (Max Scherzer)

But in baseball, how you played last year or what you were predicted to do must be balanced against how you are actually playing, in reality, right now. Both matter.

That’s a different picture. By that measure, the Nats have played winners (10-8 in games against teams with .500-or-better records this season), and the Cubs have not (5-1 in games against such opponents). The Cubs have played 20 games against losers (15-5), while the Nats have played just nine (9-0).

Those numbers got your attention? If you don’t want more stats, skip the next three paragraphs.

ERA-plus is a fine way to measure a pitcher’s value. It shows by what percentage you surpass the average league ERA (defined as 100), adjusted for home park. Bob Gibson, Roy Oswalt, Curt Schilling, Kevin Brown and Tom Seaver were all 127. That’s a wide range. The point: An ERA-plus around 125, especially for 1,000 or more innings, means you’re really good.

[On baseball: Jake Arrieta is dominating again — not even at his best]

Here are the career ERA-plus marks of the Nats’ and Cubs’ rotations. Some innings totals, such as those of Tanner Roark (401), Kyle Hendricks (283) and Joe Ross (99), are small enough that they may change utterly. Still, I wouldn’t have gotten this list remotely correct: Ross (136), Stephen Strasburg (128), Roark (127), Jon Lester (122), Max Scherzer (120), Jake Arrieta (113), Gio Gonzalez (112), John Lackey (110), Hendricks (110) and Jason Hammel (97).

The past four years as a Cub, Arrieta (42-13, 2.14 ERA) has an ERA-plus of 181! The best by any starter in history is 155 by Clayton Kershaw, then 154 by Pedro Martinez.

Often the first month of a baseball season misleads us. That may be the case again. But three NL teams — and only three — have announced themselves so far as deadly serious as well as red hot: the Cubs, Mets and Nats. All three have faced weak schedules; Baseball-Reference.com ranks them identically weak (minus-0.4 runs a game).

But until other contenders ignite and join the discussion, any and all meetings between these NL front-runners will merit our closest attention, especially because no one in the AL seems to have much of a pulse so far. Can the Nats not only survive but thrive on their road trip from hell to St. Louis, Kansas City and Chicago’s north side? Can closer Jonathan Papelbon handle the ninth inning against fine teams, not just mediocre or poor ones?

And can anyone, anyone at all, handle the apparently invincible historic Cubs, the most overwhelming World Series favorite in eons — or, at least, since the Nationals a year ago.