A pivotal series in the National League playoff race got underway today, with the Pittsburgh Pirates hosting the Chicago Cubs in the first of a four-game set. The two clubs play again tonight, with the home team now holding a five-game lead over the visitors for the top wild card spot. The St. Louis Cardinals are currently two up on the Bucs for the Central Division lead.

Theo Epstein fielded questions from the Chicago media prior to this afternoon’s affair. The subjects of chemistry and character came up, and – despite his saber chops – the Cubs president of baseball operations didn’t downplay their value. In his opinion, the youthful club he oversees is ahead of the curve when it comes to both.

“It’s impressive that they’re unfazed by the length of the season and the fact that they’re in a pennant race,” Epstein told the throng. “It’s a testament to their character. The norm is that young players — no matter how talented, no matter how great a start they get off to — tend to wither and just fade away,”

The Cubs haven’t faded away – at least not yet. Despite dropping a 5-4 decision this afternoon, they’re well-positioned for a wild card berth, Not that Epstein wants to hear it. When I brought up their proximity to the teams they’re chasing, Epstein told me and Peter Gammons that he’s more concerned about the team 6.5 games in their rear-view, the San Francisco Giants. As he echoed to the beat writers a few minutes later, “Until you get the little “C” next to your name in the standings, nothing is assured.”

He spoke from experience. In 2011, when he was the general manager in Boston, Epstein saw his team blow a nine-game lead in the final month and miss the playoffs.

As for troubled waters that may lay ahead for his current club, Epstein said that having players of high character pays dividends. In his words,“There’s going to be a time when they face adversity and have to rely on that character.”

Epstein’s concern is justified. The Cubs have lost three straight, and they play the Pirates and Cardinals – the teams with the best records in baseball – 10 more times. The Giants play 12 of their final 18 at home, all but three against teams with losing records.

What does Pittsburgh manager Clint Hurdle think about chemistry and how it applies to the teams in the playoff chase?

“At the end of the day, the chemistry – the men coming together and willing to push everything in with one common goal and not caring who gets the credit – that’s what becomes special,” Hurdle said after the game. “That’s the situation we have here and it’s the situation they have over there (with) the Cardinals. You can’t quantify how important it can be.”

What about the Cubs?

“They’re going to figure it out,” said Hurdle. “That’s the beauty of where we were a few years ago… They’ve got a really good leadership group over there that has a lot of experience in these situations, and provides direction. This is the fun part of the year for everybody. You learn every day.”

We’ll soon learn if Epstein’s Cubs have what it takes to stay the course. As for the role chemistry will play, as Hurdle alluded to, it will be hard to quantify.