In the now 21 seasons since three-divisional play and the wild card made it possible for the Cubs and Cardinals to meet in the postseason, this is the first such matchup. There have been important games between these two rivals in the past -- including this year -- but the games beginning today are clearly the "biggest" Cubs/Cardinals games ever.

There were some important games played between the two clubs in their 19 meetings during this year's regular season. Here are all 19.

April 5 at Wrigley Field: Cardinals 3, Cubs 0. ESPN brought its Sunday Night crew for the season opener at a Wrigley that had unfinished bleachers and not enough bathrooms. Then Jon Lester stunk out the joint, allowing eight hits in 4⅓ innings. It didn't matter much, as the Cubs couldn't generate much offense (five hits) off Adam Wainwright and three St. Louis relievers.

The game April 7 was postponed and rescheduled as part of a split doubleheader July 7.

April 8 at Wrigley Field: Cubs 2, Cardinals 0. On a frigid, cloudy day (mid-40s), Jake Arrieta dominated the Cardinals, allowing just three hits in seven innings. The Cubs had only two hits themselves, but pushed across two runs in the seventh, helped by two Cardinals errors, for the win. It was the first time a Cubs team had won with only two hits since September 1, 1999.

May 4 at Busch Stadium: Cardinals 10, Cubs 9. One of the worst losses of the year, the Cubs scored five in the first, then coughed four of them right back in the bottom of the inning. They extended the lead to 8-4 in the sixth, but the bullpen was awful. Addison Russell homered with two out in the ninth to make it a one-run game, but that's where it ended up.

May 5 at Busch Stadium: Cardinals 7, Cubs 4. The Cubs again had a lead in the middle innings: 4-1 entering the bottom of the fifth. Matt Carpenter hit a three-run homer to tie it, and Edwin Jackson (doesn't it feel like it's been about two years since he was a Cubs) gave up the lead in the next inning.

May 6 at Busch Stadium: Cubs 6, Cardinals 5. This was a satisfying win as the Cubs led throughout, although Pedro Strop (who had more rough outings vs. St. Louis to come) made it close by allowing a run in the eighth. Jon Lester allowed four runs, but just one was earned.

May 7 at Busch Stadium: Cardinals 5, Cubs 1. Perhaps Jake Arrieta's worst start of the year: nine hits, five runs (four earned). The offense was listless, getting only five hits off John Lackey and three Cardinals relievers.

June 26 at Busch Stadium: Cardinals 3, Cubs 2, 10 innings. Pedro Strop allowed a game-tying leadoff homer to Greg Garcia in the eighth. It was his first big-league homer after he had hit only 27 in over 2,000 minor-league at-bats. The Cardinals eventually won the game on this sequence, which ended with a throwing error by Mike Baxter, playing near second base in a five-man infield:

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June 27 at Busch Stadium: Cardinals 8, Cubs 1. Remember Donn Roach? Perhaps he's best forgotten. He threw three decent innings and then blew up in the fourth. Sent back to Iowa, he never returned and eventually was claimed on waivers by the Reds and then the Blue Jays, though he never pitched again in the big leagues in 2015. Roach singled and drove in the Cubs' only run in his sole at-bat; he is one of just seven pitchers in Cubs history to have a single at-bat for the team and get a hit in that at-bat, and the only one of those seven who drove in a run. Here are those seven pitchers.

June 28 at Busch Stadium: Cardinals 4, Cubs 1. The game was delayed almost two and a half hours by severe thunderstorms in two separate delays. There was a tornado spotted only a few miles from the stadium and fans were evacuated to the concourse. Again the Cubs couldn't generate any offense, just six hits and a run, and were outscored 15-4 in the series.

July 6 at Wrigley Field: Cardinals 6, Cubs 0. In another game delayed by thunderstorms, Edwin Jackson entered after the delay with the Cubs trailing 2-0, and promptly put the game out of reach by allowing four runs. Didn't really matter as the Cubs got just six hits off John Lackey and two relievers.

July 7, first game, at Wrigley Field: Cubs 7, Cardinals 4. The Cubs went out to an early 3-0 lead. Jake Arrieta gave up a pair of runs in the seventh. With a 7-2 lead in the ninth, Joe Maddon decided to allow Neil Ramirez to finish up, but after Ramirez allowed a two-run homer to Mark Reynolds, Maddon called on Jason Motte to finish up.

July 7, second game, at Wrigley Field: Cubs 5, Cardinals 3. The Cubs swept the day-night doubleheader. Dallas Beeler threw five decent innings and the Cubs came from behind with a three-run seventh, taking advantage of a Cardinals throwing error in the inning.

July 8 at Wrigley Field: Cardinals 6, Cubs 5. This might have been the toughest loss of the entire season, never mind against the Cardinals. Jason Hammel left the game after the first inning with a hamstring injury, and the Cubs went down 4-0 by the top of the fourth. Miguel Montero's bases-clearing double in the sixth gave the Cubs a 5-4 lead, and the cheering at Wrigley was deafening. One strike from victory and a series win, Pedro Strop served up a two-run homer to Jhonny Peralta and the Cubs lost.

September 7 at Busch Stadium: Cubs 9, Cardinals 0. The teams didn't meet for almost two full months and this September series was the most important between the two clubs since 2003. Much-maligned Dan Haren threw seven shutout innings against the team he came to the majors with, and the Cubs blasted Cardinals pitching for eight runs in the first three innings. Dexter Fowler and Addison Russell homered to lead a 12-hit attack in what was perhaps the most stunning win of the year.

September 8 at Busch Stadium: Cubs 8, Cardinals 5. The Cubs' offensive onslaught continued against Michael Wacha, who allowed six of the eight runs in four innings, the worst start of his career. Starlin Castro homered, scored three times and drove in four. It was 8-0 by the seventh; the bullpen got a bit sloppy and gave five of them back in that inning, but this game wasn't really that close.

September 9 at Busch Stadium: Cardinals 4, Cubs 3. Jon Lester allowed a leadoff triple and one-out single in the first to give the Cardinals a 1-0 lead, but then retired 20 in a row. Gassed on a hot, sticky St. Louis late-summer day, he had to leave after seven as the Cubs nursed a 3-1 lead. The bullpen imploded and allowed three runs; the Cubs could have won anyway if they'd been able to hit with RISP (2-for-11).

September 18 at Wrigley Field: Cubs 8, Cardinals 3. The Cubs struck in the first inning again, scoring three runs off Lance Lynn. Dan Haren couldn't match his performance from earlier in the month and the Cardinals tied the game in the fifth. Starlin Castro then singlehandedly won the game, and that's not hyperbole. He drove in the remaining five runs on a two-run homer in the fifth and three-run homer in the sixth.

September 19 at Wrigley Field: Cubs 5, Cardinals 4. The Cubs were sailing along with a 5-0 lead entering the ninth, thanks in part to back-to-back homers by Jorge Soler and Kris Bryant in the fifth. This was a game of beanballs after Anthony Rizzo had been hit twice the previous day. Warnings had been issued by the time Hector Rondon accidentally (yes, really) hit Greg Garcia to lead off the ninth, so he was tossed. Zac Rosscup entered and allowed a home run and two singles, leaving it up to Pedro Strop, who had been horrid against the Cardinals most of the year. He retired the next three hitters (allowing one runner to score on a sac fly) to seal the win.

September 20 at Wrigley Field: Cardinals 4, Cubs 3. The Cubs again had a chance for a sweep with Jon Lester on the mound. This time, though, Lester struggled early, allowing three first-inning runs including a pair of homers. The Cubs managed to get to within a run and got the tying run on base in the ninth on a leadoff single by Starlin Castro, but that chance was erased when pinch-runner Quintin Berry was caught stealing -- his first-ever CS in the big leagues.

The Cardinals won the season series 11 games to eight, but the runs scored were pretty even: 79 for the Cubs, 84 for the Cardinals. Most importantly, the Cubs won four of six in September, showing they could win in crunch time, and two of the three wins were in St. Louis. Hopefully, the Cubs do this weekend exactly what they did in the last series at Busch Stadium: win two straight.