Baseball was so good that day, so tense and so exciting, that a lot of people were left exhausted, sitting and staring at their television sets, unsure if they'd just seen all that happen.
That day was so much fun that Major League Baseball decided to see if it could be replicated, sort of.
So one playoff team was added in each league. With that change, more teams would be in competition, more games would be meaningful down the stretch.
All of that happened. After four months, at least 20 teams still were in contention for playoff berths. At the non-waiver Trade Deadline, it was difficult to separate the buyers and sellers because of what had happened the year before with the Rays and Cardinals coming from 10 games back in the final five weeks.
Here's the best part, the really genius part: Baseball decided the two Wild Card teams in each league would play one winner-take-all game to decide who advanced to the best-of-five Division Series.
So instead of diminishing the importance of the regular season, baseball actually increased its importance. Suddenly, there was a huge difference between winning a division championship and getting one of the Wild Card berths.
On Oct. 5, baseball gave us its first Wild Card day:
Orioles at Rangers.
Cardinals at Braves.
In a sport accustomed to the long run, to the we'll-get-'em-tomorrow attitude, this was something completely different. One game. One opportunity.
Was it as good as baseball's leaders hoped it would be? Indeed, it was. Both games were close. Both ballparks were sold out.
And in one ballpark, it was one of those nights that'll be remembered forever. It was Chipper's Last Game. It was also the Infield Fly Rule Game.
Let's set the scene.
The Braves trailed the Cardinals by three runs in the bottom of the eighth inning and had runners on first and second with one out.
That's when Atlanta shortstop Andrelton Simmons seemed to dump a base hit into left field between St. Louis shortstop Pete Kozma and left fielder Matt Holliday.
That's when it got strange.
Left-field umpire Sam Holbrook called Simmons out via the infield fly rule even though the ball was well into left field when it landed.
All heck broke loose. Fans threw debris onto the field as the game was delayed for 15 minutes.
The Braves have no idea what would have happened if they'd had the bases loaded with one out, and they'll never find out. Instead of being remembered as Chipper Jones' final game, it became a game Atlanta fans will chew on and debate forever.
For the Cards, it was a slam dunk. They loved the Wild Card format.
"There were so many teams and fan bases engaged to the last day," Cardinals manager Mike Matheny said. "This is a fan-driven business. I think the excitement level proves it was a good idea."
And then the American League Wild Card game began with Baltimore manager Buck Showalter handing the ball to Joe Saunders.
Saunders could serve as a pretty good poster boy for the 2012 Orioles, an amazing team that did amazing things.
After 15 years out of the playoffs, they won 93 games thank to a core of homegrown talent and a manager in Showalter who convinced them they were good enough to win.
Actually, Showalter demanded they believe. He got rid of some people who didn't. The Orioles won because of Adam Jones and Matt Wieters and Nick Markakis. The O's also won because no general manager did a better job than Dan Duquette.
After a decade out of baseball, he masterfully constructed a roster, and then remade the pitching staff on the fly during the season.
Saunders was one of the guys Duquette acquired. Down the stretch, Saunders had a 2.75 ERA in his final six games.
And then he went to the mound in Arlington to continue the dream. He allowed baseball's highest-scoring offense one run in 5 2/3 innings and set the tone for Baltimore's 5-1 elimination of the Rangers.
Nate McLouth, who'd been released by the Pirates a few months earlier, drove in two runs.
"Our guys approached it and we talked about it being sudden life instead of sudden death, and we played that way," Showalter said. "You've got to seize the opportunity. We don't get many."
That night, the Orioles began a wild clubhouse celebration, a celebration for both a franchise with a great history and for a city that loves its baseball team.
"We engaged the fans again," Duquette said weeks later. "It was great to see them back at the park."
There were stark emotions in the four clubhouse that evening, with the Cards and O's celebrating wildly and the Braves and Rangers bitterly disappointed.
It made for great theater, which is exactly what baseball experienced on that final day of the 2011 regular season and got again on Oct. 5.