CHICAGO -- There were a few factors behind the fist pump by Kyle Schwarber as he jogged up the first-base line in the fourth inning on Saturday night.

Not only had the Cubs slugger concluded a grueling at-bat with a home run, but his shot to the right-field stands effectively erased a rough first inning by Jon Lester. Schwarber's solo shot provided the turning point in a rousing, 9-4 comeback win over the Cardinals for the Cubs, who remain atop the National League Central.

"There's no quit here," Schwarber said. "We know with a couple swings of the bat we're right back in the game."

• Box score

Chicago scored nine unanswered runs to take Lester off the hook and send him on his way to the win column. The victory marked the sixth in a row over the rival Cardinals at Wrigley Field, and the Chicago crowd became more rowdy as the evening wore on and the runs piled up.

Here were the three keys to the Cubs' stirring comeback:

1) Lester's quick adjustment
Lester admittedly got caught up in the walk he issued to Paul DeJong two batters into the game. The veteran said he lost his focus following that damaging free pass and then that had a carryover effect through the next two batters he faced.

Paul Goldschmidt followed with a single up the middle and then Marcell Ozuna pounded a 3-0 fastball to the back of the batter's eye in center field for a three-run homer.

"The Ozuna at-bat," Lester said, "it's something that I'm definitely going to lose sleep over."

Two batters later, Harrison Bader ambushed a first-pitch fastball, sending it over the left-field bleacher seats to give the Cardinals a quick, 4-0, advantage. Lester said he could live with that type of home run, but the sequence of events earlier in the frame gnawed at him. So, the left-hander needed to make a change in the name of survival the rest of the way.

"I didn't have a choice," Lester said. "I just had to make the adjustment of trying to get weaker contact."

During that first inning, Lester fired his four-seamer 15 times. He only used that pitch nine more times over the next five frames. Following a two-out single by Kolten Wong in the first, St. Louis went 1-for-17 the rest of the way against Lester, who did not have a ball in play leave the infield during that stretch. In fact, the Cardinals did not hit a ball to the outfield the rest of the night.

"They were on everything," Cubs manager Joe Maddon said of the first inning. "But honestly, it was the pitch selection that wasn't very good. We just pitched into their strengths. I think that was what was going on, because you saw, as the game was in progress, the same hitters had a more difficult time."

2) Schwarber's 11-pitch blast
More than in any game his season, the Cubs' batters were willing to wait for their pitch on Saturday night.

Chicago's lineup forced the Cardinals to throw 192 pitches over eight innings. Pitch data only goes back to 1988, but there have only been five games on record at Wrigley Field that included at least 200 pitches by the opposition in fewer than nine innings. Chicago was not in the mood to chase on this night -- as evidenced by Jack Flaherty having no strikeouts in his abbreviated outing (3 2/3 innings).

"I saw a lot of mental situational hitting going on today," Maddon said. "That's what we need to do more often."

That was on display in extreme fashion in the fourth inning.

With two outs, Schwarber and Flaherty locked horns for 11 pitches. The Cardinals pitcher mixed things up for the first seven, giving the Cubs slugger three four-seamers, three curveballs and one slider in that stretch. Flaherty went inside and he elevated. He tried to entice with something low and away.

From the eighth pitch on, Flaherty attacked Schwarber with four straight heaters.

"That’s just what I felt what was the best way to get him out," Flaherty said. "Kept getting in there, kept getting in there, then one left over the middle. Poor execution on the last one."

After fouling off five pitches in a row, Schwarber sent the last one deep into the night with an exit velocity of 114.7 mph, per Statcast. After the Cubs rallied for two runs in the first and one more via a fluky, run-scoring triple by Javier Baez in the third, Schwarber's blast pulled the game into a 4-4 deadlock.

"Schwarbs, that's what it's supposed to look like," Maddon said. "And not because of the home run. What he's doing at the plate right now, we need to keep that in the jar, because that looks really good."

3) Caratini's pinch-hit heroics
Helmet on and bat in hand, Lester was standing in the on-deck circle in the sixth inning, preparing to hit after Albert Almora Jr. That plan changed right before Almora sent a pitch from reliever John Gant into center field for a single that loaded the bases with no outs.

The Cubs manager summoned backup catcher and switch-hitter Victor Caratini off the bench, ending Lester's night. Part of the reasoning was that St. Louis did a double-switch when Gant entered the game. With the game still tied, now the Cardinals would have Dexter Fowler due to hit second -- not the pitcher -- in the top of the seventh.

"You've got to do something at that juncture," Maddon said.

Caratini wasted no time.

Gant fired a first-pitch fastball and Caratini sliced it into left field, where the ball tailed away from Ozuna. The left fielder made a sliding attempt to catch up with the sinking liner, but the baseball dropped in and skipped to the wall. All three runners were off to the races, with Almora losing both his helmet and headband between second and third as he hustled for home.

Three runs scored, and the Wrigley Field crowd erupted.

"I knew going into the inning that there was a good possibility that I was going to pinch-hit," Caratini said through a team interpreter. "That gave me the time to get ready both physically and mentally. ... [You are] acting as if it's your third or fourth at-bat of the day and staying aggressive. I think that's the key. At least for me."

That put both the Cubs and Lester on the path to the win.

"'Tini with the big hit in the sixth there," Lester said. "That was big for us."