But a spark -- and then some -- was what they got in a 14-7 victory at Cincinnati.
Making his major league debut, the 20-year-old Castro hit a three-run homer in his first major league at-bat and later added a three-run triple. The six RBIs in a debut established a major league record.
The Cubs said they wanted to reward Castro for a good start at Tennessee and to shore up their middle-infield defense by moving erstwhile shortstop Ryan Theriot to second base.
"I hope generally it helps," said general manager Jim Hendry. "Sometimes you make changes, and that happens. Hopefully the young man gets off to a good start. We're certainly not going to put a lot of pressure on him to do that. We just want him to come up and play good defense and let the offense take care of itself."
The Cubs had just come off a three-game sweep at the hands of the Pirates in Pittsburgh, having scored five runs in three games.
At Tennessee, Castro batted .376 with one homer, eight doubles, five triples and 20 RBI.
Manager Lou Piniella put Castro in the eighth spot in the batting order and said he'll let him get his feet wet there for a while.
CUBS 14, REDS 7: In addition to Castro's effort, right-hander Carlos Silva survived five innings, giving up 10 hits and four runs to improve to 3-0.
--Castro received word Friday morning at 7 a.m. that he was coming up from Tennessee to the big leagues.
"When the manager called and said, 'You made the majors,' I said, 'Are you serious?'" Castro said. "I said that. I didn't believe it."
Castro may have sparked the same reaction by those who watched him after he arrived.
Theriot took over as Cubs shortstop in 2007, and he said the move to second base to accommodate Castro at short was OK with him.
"We're excited to have him, and I'm going to do everything I can in my power to make sure he's comfortable, to make sure this transition is a smooth and easy one for him," Theriot said. "The same way guys did for me."
Theriot entered this year with 79 games of big league experience at second base.
Chad Tracy was optioned to Class AAA Iowa to make room for Castro. Tracy had played a utility role in the first month and batted .273 (6-for-22) with two RBI. Piniella said Tracy did a "representative job" in his time up. He signed a minor league deal in the offseason and came to spring training as a non-roster man.
Jeff Baker and Mike Fontenot now assume utility roles, according to Piniella. The two had shared second-base duties before Castro's call-up moved Theriot to second. Baker can back up Aramis Ramirez at third base, and Fontenot now is the primary backup shortstop as Piniella said he will not move Theriot back there. Fontenot hit a pinch grand slam against the Reds. It was the Cubs' first pinch-hit grand slam since Derrek Lee did it against the White Sox on May 19, 2007.
--Silva complained of tightness near the point where his neck and right shoulder meet. He threw 92 pitches in five innings and said the ailment was nothing serious. He had been bothered by back stiffness in an earlier start.