Jackson, the No. 1 Draft pick in 2009 and ranked as the Cubs' top prospect, was inserted into the lineup in the No. 2 spot Sunday against the Dodgers and finished 2-for-4 with a pair of singles and a run in the 7-6 loss. He'll play 80 to 90 percent of the time, Cubs manager Dale Sveum said, with Vitters sharing third base with Luis Valbuena. A right-handed hitter, Vitters will most likely face left-handed pitchers.
Jackson was batting .256 with 15 home runs, 22 doubles, 12 triples, and 158 strikeouts in 106 games at Iowa. The strikeout totals are high, but Jackson, who fanned 50 times in June, trimmed that number to 36 in July, and has shown improvement.
"His OPS with those strikeouts is incredible," Sveum said. "The reason we decided to finally get him here is to evaluate him here and get his development started here at the big leagues and see what happens just to help us defensively and things like that."
The Cubs are hoping that having Jackson work with Sveum and hitting coach James Rowson they will see more progress.
"[The strikeouts] have to come down for him to have success as a big leaguer, and he knows that," Cubs general manager Jed Hoyer said.
Yes, he does.
"I knew how close I was and I pushed myself a little too hard to be here," Jackson said. "I'm here now, and I'm going to play my guts out and my heart out every day, that's the type of player I am and that's the type of player I'll always be."
It was perfect timing for Jackson, whose family was in the Southern California area watching his brother play in a tournament. He had to leave about 25 tickets
Vitters, the top pick in the '07 Draft and the team's No. 11 prospect, was hitting .304 with 17 home runs, 32 doubles and two triples in 110 games. The third baseman hit a three-run homer in the eighth inning on Saturday night for Iowa and stole a base. The only questions have been about Vitters' defense.
"He's having a real good year, and his defense is the thing he has to work through," Hoyer said.
Vitters, who grew up about 30 minutes from Dodger Stadium in Anaheim, had about 12 friends and family members at the game.
"I didn't want to overdue it -- I didn't want to invite the whole city," he said.
He didn't get to start against the Dodgers, just soak in the action from the dugout until the seventh.
"I was more nervous before the game than I was when I got the uniform on and went out there and got an at-bat," said Vitters, who flied out to left in a pinch-hit at-bat.
He was motivated this year.
"I had a goal in my mind," Vitters said. "I had a goal that I wanted to be here. I did everything I possibly could. I looked at myself as a player and I wanted to improve all of my weaker points and make them better and improve my strong points as well to make me a better all around player. I think the dedication paid off."
The Cubs were able to make the moves after trading utility infielder Jeff Baker to the Tigers. Tony Campana was optioned to Iowa to make room.
"It's been a crazy 12 hours since I found out," Jackson said. "It's good to be here, and I'm excited to be in the lineup."
It was a long morning as Jackson and Vitters grabbed a 6 a.m. flight from Des Moines to Dallas, then arrived in Los Angeles in time for some quick batting practice. There have been rumors of Jackson's arrival in recent days.
"I tried to keep my head out of it," Jackson said. "For the most part I've been working and pushing myself to be in the right shape for when the time came."
The Cubs are hoping both can have a little quicker success than Anthony Rizzo did when called up last season with the Padres. Rizzo batted .141, went back to the Minors this season and has posted impressive stats since his callup June 26. He was named National League Rookie of the Month in July.
"I think it'll be a good experience for both of these guys," Hoyer said. "They get a chance to come up and get a taste of the big leagues. They can help us win for sure and they also can figure out what they need to do up here to have success. If they have success, wonderful, and if they struggle a little bit, hopefully they'll learn from those struggles and spend the offseason learning from those things.
"I don't see a downside for either of those guys as far as their development goes in coming up here and experiencing what the big leagues is about."
Jackson was eager to get started. Last year, he was batting .256 at Double-A Tennessee, then promoted to Iowa and batted .297.
"I can promise I'm going to play the game as hard as I always do, and I play to win, and that's the type of player I am and that's the type of player I'll always be," Jackson said.
The two sat next to each other on their flights Sunday.
"I like to say I've taken him under my wing as a little brother, and I have some stuff I've learned from him about hitting this year -- that guy can hit," Jackson said of Vitters. "I'm excited to get it started now."
Unfortunately, his first at-bat wasn't one to remember as he grounded out to first, advancing David DeJesus, who had walked. There was some confusion as Jackson thought he fouled the ball. He'll get more at-bats.
It's not just time to see Jackson and Vitters in the big leagues but also a chance to improve on the Cubs' outfield defense and offense. They're 0-4 since the Trade Deadline, and the offense has not shown many signs of life. Chicago has scored two runs in two games against the Dodgers.
With the moves, the rebuilding starts in earnest.
"For this year, when we went into the season, the three position players were Vitters, Jackson and Rizzo," Sveum said. "They've done their development and now it's time to see and develop a little bit at the big leagues and see what we have going into the winter and what they have to work on.
"Hopefully, they excel and might not have to work on anything," Sveum said. "We're at that point in the organization where we've got [Alberto] Cabrera here now, another power arm we really liked. He probably got here quicker than we thought. Other than that, we've got most of the guys here who we liked in Spring Training and have a chance to produce and help the Major League in the future."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.