CINCINNATI -- The struggling Chicago Cubs called up top prospect Starlin Castro on Friday, and his debut could not have gone better.
The 20-year-old, who became the youngest shortstop in franchise history, homered, tripled and drove in a record six runs in the Cubs' 14-7 victory over the Reds on Friday night.
In his first big-league at-bat in the second inning, Castro powered a 2-2 pitch over the fence in right-center field for an opposite-field, three-run shot.
He became the sixth player in Cubs history to connect his first time up. The last to do it was Jim Bullinger in 1992.
Castro came up in the fifth with the bases loaded and hit a triple to left-center field. The liner came on a full count and gave the Cubs a 9-0 lead.
That gave Castro the major league record for RBIs in a debut with six, and the game was still in the fifth inning. The previous record was five RBIs, held by four players and most recently accomplished by Ben Grieve for Oakland in 1997.
Even Castro's out in his second at-bat on Friday was impressive. Castro scorched the first pitch hit he saw in the fourth into center field, but Drew Stubbs made a sliding catch coming in. Castro fouled out to first in his fourth at-bat in the seventh.
Castro became the third youngest in major league history to homer in his first at-bat. The two younger players were Whitey Lockman (age 18) in July 1945 and Ted Tappe (age 19) in September 1950.
He finished 2-for-5 on the night.
Castro made the jump from Double-A Tennessee, where he was asleep after a night game when the phone rang at 7 a.m. The Cubs' top-rated prospect didn't expect to be in the majors until much later in the season.
A few hours later, he was in Cincinnati and in the starting lineup for a game against the Reds, batting eighth. The Cubs hoped to just get him acclimated, but he gave them a 3-0 lead with his blast.
"I'm happy. Whoo!" he said, sitting in his locker before the game with a No. 13 jersey hanging from the side.
Castro became the youngest Cub to make his big-league debut since Oscar Gamble did it at the age of 19 in 1969. He was also the youngest shortstop to make his debut with the Cubs.
Chicago optioned infielder Chad Tracy to Triple-A Iowa to make room on the roster. Tracy opened the season with the Cubs and batted .273 in 19 games.
"We're excited about bringing Starlin to the big leagues," Cubs general manager Jim Hendry said. "He played awfully well at Double-A.
"We also felt that at this time, he would make our team better defensively. At the same time, we feel Ryan [Theriot] will be better served playing on the other side of the bag, where he has a lot of experience as well."
The Cubs made the move after they got swept in a three-game series in Pittsburgh, dropping them to 13-16 -- good for fourth place in the NL Central.
"I made this decision a couple of days ago," Hendry said. "We haven't knocked in runs, so the decision is that we should make the team better defensively.
"By bringing Starlin up and playing him at shortstop, we feel we are better there and at second base."
It's the second major move the Cubs have made to try to get their season turned around. Manager Lou Piniella shifted ace Carlos Zambrano to the bullpen on April 21, trying to fix their biggest problem at that point. A shaky bullpen had threatened to scuttle their season less than a month into it.
The bullpen has improved with Zambrano. Now, the Cubs have to do something to improve the everyday lineup for now and later.
"Look, can't look at this thing day-to-day," Piniella said. "It gets too tiring. It gets too cumbersome. You've got to look over a period of time. You've got to look at things with a little longevity to them. That's what we're doing with this move."
Castro went to spring training with the Cubs, wearing No. 67. He expected to spend most of the season in the minors, but sped up the process by batting .376 with eight doubles, five triples and a homer in 26 games at Tennessee.
When he got awakened by the call to the majors, he was surprised.
"I said, 'Are you serious?'" Castro said.
He then called his family and friends in the Dominican Republic. The native of Monte Cristy signed with the Cubs as a free agent on Oct. 25, 2006. He batted .310 with 48 doubles, 18 triples, 9 homers and 122 RBIs in four seasons in the minors.
Piniella was impressed by how Castro handled himself during spring training, when the shortstop turned 20.
"This spring if you didn't mention that he was 19 years old, you couldn't tell it by the way he handled himself," Piniella said.
Piniella had a talk on Friday with Theriot. Theriot became the Cubs' everyday shortstop in 2007. He started 147 games there last season, the most by a Cub since Shawon Dunston started 150 games at shortstop in 1988.
Theriot has played in 79 games at second base during his career.
"He's played there before," Piniella said. "He had a little workout there this afternoon and we'll throw him into the fire."
ESPNChicago.com's Bruce Levine contributed to this report.