CHICAGO -- In the Cardinals’ biggest game of the year so far, Matt Carpenter was the one who seized the moment.

On the first pitch he saw from Cubs closer Craig Kimbrel in the top of the 10th inning, he launched a no-doubt home run to dead center field, giving the Cardinals a 5-4 victory on Thursday night at Wrigley Field.

• Box score

It was a crucial win to start an important four-game series and seven-game stretch against the Cubs that spans 10 days. St. Louis won its first game at Wrigley Field this year, kept its three-game lead in the National League Central over Milwaukee and pushed Chicago to four games back.

• NL Central standings

“We’re getting close to sealing the deal, but every day is important,” Carpenter said. “We have to focus on each day. I’m certainly anticipating every game to be like this. [The Cubs] never quit, they are a great team, and they fought us to the end. We’ve got to be ready to go each night, because I think they’re all going to be just like this.”

Thursday’s atmosphere embodied the pennant race. Inside a packed Wrigley Field, Cardinals starter Jack Flaherty dealt for eight innings, allowing just one run on three hits while striking out eight. The Cardinals’ 23-year-old starter has a 1.05 ERA since the All-Star break and stifled a strong Cubs lineup.

“It definitely felt like a playoff atmosphere,” Flaherty said. “I’ve never been in that kind of situation before, so that’s about as close as we can get.”

After Flaherty’s eight strong innings, Cardinals closer Carlos Martinez walked the leadoff batter in the ninth and allowed three singles to bring the Cubs within one run with one out. Andrew Miller got out of the inning, but not without the tying run scoring and sending the game to extra innings.

Carpenter quickly returned the momentum to his club in the 10th. As the ball sailed over the wall, Carpenter looked at the overjoyed Cardinals dugout and pointed to his teammates.

“Just excited for our group of guys,” Carpenter said. “It was a gut punch the inning before. Jack pitched so great. We had the game locked, and it squeaked away from us. They tied it up, and just the emotional turn to get the lead again. I was looking in there, the excitement, I was fired up for everybody.”

While the Cardinals’ focus is on one game at a time as the postseason nears, Carpenter has kept his focus on the present, too. The third baseman has struggled this season, posting career lows in average, on-base percentage and slugging. Tommy Edman has taken over third base, while Carpenter has been used as a pinch-hitter or late defensive substitution.

“How can I help our team each day, in whatever role that is?” Carpenter said. “Really not worried about the past or how it’s played out to this point. Just focused on what I could do today in this moment.”

That moment was in the fifth inning on Thursday, when Kolten Wong strained his left hamstring while running to first base. Edman moved to second as Carpenter ran out to third. He struck out swinging in the seventh inning in his first at-bat, but he was ready for the fastball Kimbrel threw down the middle the next time he came to the plate.

• Wong exits early with left hamstring injury

The 431-foot home run was a reminder of the player that Carpenter has been and how he still has a big impact on a team fighting to get back to the playoffs. For Cardinals manager Mike Shildt, it was evidence of the kind of swings he’s seen Carpenter take in batting practice and in pinch-hitting situations lately.

“He’s seeing the ball better,” Shildt said. “He’s on time. He’s connected with everything he’s doing. We’ve had some really positive talks with Carp, and his mindset is, ‘I’m going to take care of today and I’m going to be ready to go moving forward for whatever role that looks like.' Clearly, he backed his word up.”