The Cubs, who are second in the National League Wild Card standings, have two weeks to go in the regular season and are 36-16 since July 27, the second-best record in the Major Leagues, behind the Blue Jays. They took two out of three at Busch Stadium and again at Wrigley Field against the Cardinals, who have the best record in baseball.
"I think we're a lot better now than we were earlier in the season," Epstein said. "We're playing good baseball, and you want to play teams like [the Cardinals] when players are feeling good about themselves."
Plus, the Cubs nearly swept the weekend series from the Cardinals, but an eighth-inning rally fell short.
"Look what it takes to beat us right now," Epstein said. "You've got to show up and do a lot of things right to beat us right now the way we're playing. It's on us to keep playing that way."
Thanks to such late-season additions as Austin Jackson, Javier Baez and Tommy La Stella, manager Joe Maddon can adjust his lineup for the best matchup. Epstein likes the depth and said this "second wave" of players has been an important element.
But the biggest factor has been the fast-paced development of the young Cubs: Kris Bryant, Addison Russell and Kyle Schwarber. Epstein said it's a challenge to create an environment at the Major League level that allows young players to relax, and credits Maddon with doing just that.
"The guys like being around [Maddon]," Epstein said. "They feel they can be themselves. It's fun to come to work every day, it's fun to be around him. That environment has really accelerated the process with these guys, to not just be big leaguers but [to be] good big league players. We wouldn't be where we are without the contributions of a lot of first- and second-year players."
If there is a concern, it's the rotation. Jake Arrieta, who will aim at his 20th win on Tuesday against the Brewers, and Jon Lester have been consistent.
"You want to see guys get some momentum and pitch well down the stretch," Epstein said. "We know it's in there."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings. You can follow her on Twitter @CarrieMuskat and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.