CHICAGO -- The Cubs' kids are growing up quickly.

Rookies Tyler Colvin and Starlin Castro each hit home runs, and freshman Andrew Cashner shut down Albert Pujols in a key at-bat to lead the Cubs to a 6-5 victory on Saturday over the division-rival St. Louis Cardinals.

Tom Gorzelanny (6-5) benefited from the power surge to improve to 4-0 since returning to the rotation. In his last five outings, the lefty has given up nine earned runs over 28 2/3 innings for a 2.83 ERA.

"There's no reason this young man can't hold down a rotation spot in a Major League rotation for this organization and pitch well," Cubs manager Lou Piniella said of Gorzelanny. "He's young and he's durable, and he's got the pitches. It's just a question of having the confidence, and I think you're seeing the confidence manifest himself."

The same can be said of the three rookies. Colvin got things started with his second leadoff homer in as many games. He's the first Cubs leadoff man to connect in consecutive games since Alfonso Soriano did so May 13-14, 2008, against San Diego. Colvin now has 15 for the season, the most home runs by a left-handed-hitting Cubs rookie since Mel Hall belted 17 in 1983. The team mark is 25, set by Hall of Famer Billy Williams in 1961.

"Once he learns the strike zone and lays off bad pitches, he's got the power, he's got the ability to hit left-hand pitching, which is important, and he can hit in the middle part of the lineup," Piniella said of Colvin, who batted leadoff for the 10th game. "He needs to keep improving, but he's a good looking young talent."

"It's not just learning the strike zone," Colvin said. "It's learning what to swing at. I feel I can hit stuff, but just because I can reach it doesn't mean I can hit it well. It's a matter of going out there and looking for pitches I can handle instead of swinging at sliders down and away that I can't do anything with."

And the home run he hit?

"[The count] was 3-2, so anything close -- I didn't want to strike out there," Colvin said. "I just went down and got it, and it went up in the wind."

The Cardinals went ahead, 2-1, in the second, but Colvin walked with one out in the third and Castro followed with his third homer off the first pitch from Blake Hawksworth (4-6).

"It's a good percentage that every home run I hit will be on the first pitch," Castro said. "I like to swing at the first pitch."

He finished with three hits and missed hitting for the cycle by a triple. In his last 11 games, the 20-year-old shortstop is batting .489 (22-for-45) with seven doubles, a triple, a home run and eight RBIs. What's impressed Colvin about Castro?

"His ability to adjust so quick," Colvin said. "He's hitting every ball hard that he puts in play. That's what I'm used to seeing from last year [at Double-A Tennessee]."

In the Minors, the two also batted at the top of the order, although for one month, Castro was leading off and Colvin hitting second. It doesn't seem to matter.

Marlon Byrd added a RBI double in the Cubs' third to make it 4-2, but the Cardinals closed to 4-3 in the fifth on Jon Jay's sacrifice fly.

The Cubs loaded the bases with one out in their half against Mitchell Boggs, who bounced the ball in on a 2-0 pitch to Soriano. One run scored on the wild pitch, and another tallied on catcher Yadier Molina's errant throw.

"We had one tough play, bases loaded, and that ball doesn't get by Yadier very often," St. Louis' Aaron Miles said, "but that's baseball. It happens. We couldn't capitalize enough on their mistakes."

Such as Ryan Theriot's wind-aided error in the eighth, which led to another St. Louis run. The Cardinals had the tying run on in the seventh, eighth and ninth innings. Cashner escaped the eighth by getting Tyler Greene to hit into a game-saving double play.

Go back to the seventh. The Cardinals had two on, nobody out and Pujols up. Cashner fired three straight 100-mph fastballs after the count reached 3-2. The Cardinals slugger fouled the first two off and ended up with a sacrifice fly.

Cashner's plan?

"Not giving in," the reliever said.

The rookie right-hander wasn't feeling well before the game, coughing up phlegm. That didn't stop him from dealing against Pujols.

"He's one of the best hitters in the game," Cashner said. "If I'm going to get beat, I'm going to get beat with my fastball with him."

"He's mature beyond his years," Theriot said of Cashner. "He's aggressive. He's not afraid to shake off a pitch. What I've noticed is a lot of young pitchers, they just throw whatever sign is put down. [Cashner] has a plan, and he's executing that plan."

The same could be said for Colvin and Castro.