The Cubs have already proved to the rest of the baseball world that they're legitimate contenders.
Now they've proved it to the Cardinals, as well.
The Cubs couldn't complete the sweep against St. Louis Sunday afternoon at Wrigley, but the 4-3 loss doesn't change the fact that they now have the belief they can stand toe-to-toe with - and beat - the best team in baseball.
"I could not be more proud of our guys," Cubs manager Joe Maddon said. "It's obvious that we're playing on the same level as they are right now. I'm really proud of our guys for that.
"How far we've come in one season to get to this particular game today. Give them credit. They are very good, also.
"But I think now, we know we can beat them and they know we can beat them, too. And that's a good thing."
Before the Cubs went down to St. Louis for a three-game series with the Cardinals earlier this month, Maddon preached the importance of beating the NL Central leaders on their home field and closing out games when they have the lead.
Now, after the three-game series at Wrigley Field, the Cubs have proved their worth by winning four of the six games against the Cardinals and coming up just short on the two losses.
"We're up. Gotta look at the positives," Jon Lester said. "Obviously we would have liked to win all six games - we had an opportunity to. But at the end of the day, that's a good team across the way and they don't give outs up.
"We're playing good baseball the last six games against them. Maybe proving to ourselves a little bit that we can compete with these guys and can even beat 'em."
The Cardinals took a page out of the Cubs' book and jumped all over Lester in the first inning of Sunday's game, scoring three runs on a pair of homers from rookies Tommy Pham and Stephen Piscotty.
St. Louis right fielder Jason Heyward erased a Cubs threat in the eighth when he gunned down Anthony Rizzo at the plate on Addison Russell's fly ball. In the ninth, the Cardinals halted another Cubs rally when pinch-runner Quintin Berry was thrown out trying to steal second base, his first caught-stealing of his major-league career (he had been 25-for-25 prior to Sunday).
Any illusions the Cubs had about winning the division were essentially dashed with Sunday's loss. Instead of being four games back with a sweep, the Cubs are now six games behind the Cardinals with only 13 left to play.
[NBC SHOP: Gear up, Cubs fans!]
Which means the Cubs and Pirates are still on a collision course to square off in the wild-card game ... but will that winner-take-all contest take place in Pittsburgh or on Chicago's North side?
The winner will move on to play the Cardinals in a best-of-five series.
"I think these last six games [against the Cardinals] have really helped guys as far as confidence and just trying to get over that hump of beating these guys," Lester said.
"If we get fortunate enough to face these guys [in the NLDS], we'll be right there with 'em."