Gradually, one piece at a time in five interwoven installments, this World Series has turned into one of the finest in many years. Little was expected perhaps. Much has already been delivered. And even more is now promised as Game 6 returns here on Wednesday with the Cardinals clinging to life.

The best World Series develop their themes and isolate unexpected key protagonists as they progress organically. The dramatic tension is created spontaneously, not pre-scripted as a ratings-dream Phils-Red Sox Series might have done. Every night, this Series is completely fresh, unexpected and revelatory. All predictions have been turned to kindling and set ablaze. The most important features of every game have been a complete surprise.

All that’s certain is that you won’t get what you expect. Unless you thought Mike Adams, 41-year-old Darren Oliver and Lance Lynn would all be winning Series pitchers. Or that Cardinal Allen Craig facing Alexi Ogando would be this Series’s recurring electric late-inning showdown.

We may see 4-2, 3-2 or 2-1 with late-inning comeback victories. With such narrow margins, something as subtle as a missed cutoff throw or a mumbled name in a phone call to a noisy bullpen may actually be The Thing that turns a World Series game. Or we may see 16-7 with every meaningful one-game Series hitting record smashed by the best (honest) batter since Ted Williams.

We learn to love Mike Napoli, a bounce-around veteran catcher with a big bat, who has finally found a team that adores him. Now, sweaty, hat backward, wearing distressed fatigues to news conferences, he has nine RBI, five runners thrown out stealing and a nation chanting “MVP” for him.

Rays Manager Joe Maddon said it first when the Texas catcher wrecked his club: “This is the Year of the Napoli.” We’re all Napolitans now.

We thrill for a nervous young southpaw, Derek Holland, patted on the cheek by his manager before he takes the mound, as he masters himself and pitches a two-hit gem when it’s desperately needed.

We see the value of the simple kindly touch, the gift for grasping personality under pressure, when Ranger Manager Ron Washington repeatedly knows how to calm and motivate his players. Most managers with a three-games-to-two lead pretend that no Game 7 could ever happen or that it’s a state secret whom he’d pitch if there were.

Instead, Washington, who dances his runners home on his tippy toes in the dugout, sees an opportunity to instill confidence. Under any and all circumstances, even if Game 6 is rained out Wednesday, Washington says that Matt Harrison, who was stage-struck awful in the 16-7 massacre, would start a winner-take-all game.

“That’s Harry’s game. Matt Harrison earned it,” Washington said. “That’s the way we roll.”

We discover that Cardinals Manager Tony La Russa can preside over colossal blunders, then man up the next day and admit his responsibility for the mess.

“Not to have the right pitcher ready [in the bullpen] when you want him . . . You go and make a pitching change, [and] you’ve got the wrong guy coming out there, that’s not fun. Geez, that was embarrassing,” said La Russa, the most famous bullpen-ringer on earth, who spent the entire, game-turning eighth inning hashing up every phone call. “It’s my fault for not handling it better.”

We gasp at Albert Pujols’s ability to go 5 for 6 with three homers and six RBI in one game, yet continue his career-long Series problems in every other game, including two nights when he played a central role in a loss. La Russa and Pujols, the only two men here who seem certain to end up in Cooperstown, are running neck-and-neck for Series goat if the Cards lose.

But perhaps none of this is the absolutely best feature of this Series. What’s most fun is the doubly dramatic backdrop of two entirely opposite franchises — both with a chance for their most unique achievement. The Rangers, formerly the Washington Senators, have never won a world title in the franchise’s 50-year history. That’s a cut-and-dried kind of October joy.

The Cardinals have won 10 titles and 18 pennants. But never have they had a chance to do something as unique as they could if they win two more games in their home ballpark.

Considering their blunders in a mortifying Game 5 loss, if the Cards can shake off such corrosive memories and win this Series, they will almost certainly be remembered as the most amazing, improbable comeback team ever to win a world title, topping a tiny handful of worthy rivals: the ’14 Miracle Braves, the ’78 Yankees and the ’04 Red Sox.

Our era has lots of trouble with the word “greatest.” We love to apply it to anything that catches our eye, so long as it happened recently. But we’re seldom discriminating. We’ve lost the habit of perspective. As a result, when something that actually might be the “greatest” of its kind arrives, it can be standing in front of us and we lack the frame of reference to recognize it.

If the Cards collect themselves and win these last two games at home — and in identical circumstances, that exactly what the ’02 Angels and ’01 Diamondbacks did — we’ll have plenty of time for comparisons.

Will we see a Game 7 with all those possibilities piled high?

This wasn’t the fancy, high-toned World Series we were supposed to want to see. But it’s the one we got, and it’s starting to feel special indeed. Lest anyone think the Cards have folded, here’s the way ace Chris Carpenter recalls the famous team meeting on Aug. 25 that coincided with St. Louis’s amazing comeback from 10½ games out of the wild-card spot.

“There was a lot of angst . . . in our clubhouse with the race, with our team and the expectations,” Carpenter said. “We didn’t want to lose those expectations, even though everybody else had written us off. We might not catch Milwaukee, we might not catch Atlanta, but let’s go ahead and do everything we can to not embarrass ourselves. Let’s not embarrass our coaches. Let’s not embarrass our organization and our fans. Let’s go at least make it look respectful.”

Perhaps he meant to say “respectable.” But it’s a fine Freudian slip. Respect for the game, and for your own talent — regardless of the standings, regardless of probabilities, regardless of whether your effort “means” anything except that you dug down and gave it — is one of baseball’s richest cores of value.

The idea that the Cardinals, regardless of their disappointments in the last two games, would crumple when they are so close to such a goal seems implausible. Who wins we can’t know. But with these five superb games as a preamble, it seems unlikely that this World Series will go out with anything less than a suitably spectacular last act.