Rizzo, the highly touted first baseman who went 2-for-4 Tuesday in his Cubs debut, hit .313 against left-handers at Triple-A Iowa. That's one reason Sveum left him in the No. 3 spot.
"You want to get some stability in this lineup," Sveum said Wednesday. "You call people up who are going to be here a long time, you just want to leave them alone. [Starlin] Castro and [Rizzo], we'll see what happens. I don't want to keep moving things around, because then you can't protect this guy or that guy, and it snowballs into another problem. We're committed to this lineup and lefties will be what they are. Those two guys will be in the same spot from now on."
Castro has batted .311 in 24 games in the No. 2 spot and .296 in 50 games in the No. 3 spot this season.
"We've tried to mix and match and tried to figure something out to create some offense," Sveum said. "Now, you've got a third hitter and a second hitter and it's pretty much going to stay that way for the rest of the year."
Rizzo, 22, was able to get his pregame work done without being followed by cameras on Wednesday, and said he didn't think it would be difficult to maintain his routine.
"It's just about getting comfortable now," he said. "It's just going day by day and working my tail off."
For Rizzo fans, note that he doesn't have a Twitter account.
"I did have one but I shut it down -- too much for me to handle," he said.
And what about wearing No. 44? That was the number the Cubs assigned him in Spring Training. He wore No. 27 with the Padres.
"Forty-four, they gave it to me in Spring Training, and it grew on me," he said.