On Tuesday, LaHair delivered a leadoff homer in the ninth off the Cardinals Marc Rzepczynski for his first hit off a lefty in seven at-bats. Alfonso Soriano's walk-off single an inning later gave the Cubs a 3-2 win.
So far, Jeff Baker has started at first base against left-handed starters, while LaHair has faced more righties. The latter finished Tuesday hitting .424 (14-for-33) against right-handers; the former entered the day with a career .309 average against lefties and was 2-for-8 this season.
"I'm not afraid of left-handers," LaHair said before the game. "I feel any time I come to the plate, I can do something, whether it's lefty or righty. I'm on board [with sharing first]. I have a role and I've accepted it."
Cubs manager Dale Sveum said he didn't consider lifting LaHair for a pinch-hitter in the ninth on Tuesday.
"You do want to give him at-bats against lefties, you don't want to straight platoon," Sveum said. "The bottom line is Baker swings the heck out of the bat against left-handed pitching and you have to give him at-bats and sometimes without jeopardizing our defense in other areas, that's the one spot Baker is going to play."
Someday, LaHair may have to make room for first-base prospect Anthony Rizzo, who finished the day batting .373 with seven home runs at Triple-A Iowa.
"I've been following him, and I know he's doing well," LaHair said. "That's to be expected. The kid can really hit, there's no doubt about it. I know he's down there working on some things and trying to make adjustments. I've been there before. He's going to figure out that little part that he needs to figure out, and I'm sure he'll have a lot of success."
LaHair said he feels comfortable in the outfield, so if the Cubs ask him to move over to make room for Rizzo, he would do it. Right now, LaHair doesn't plan on stepping aside.
"This is my opportunity," LaHair said. "It's something I've visualized my entire life. I've been seeing myself do this for a while."
A few years ago, LaHair was more of a free swinger. He'd like to have more at-bats like he did Monday night against Jason Motte, when he drew a walk after 12 pitches from the Cardinals' closer.
"I'm more consistent now, I know what I want to do," LaHair said. "I simplify as much as I can. If it's not the pitch I'm looking for, I try to take it, but it's not always that easy.
Since making his debut with the Cubs on Sept. 4, LaHair has averaged 4.20 pitches per plate appearance, which is fifth among National League hitters in that span.
"I'm still going to strike out -- I'm not up there to walk, at the end of the day," he said. "At this level, it's important to get on base and keep the line moving. Wearing down the pitcher is a big part of it, too. If they throw me a cookie on the first pitch for 10 at-bats, I'm going to swing at it. If I ground out 10 in a row, it is what it is. I'm just trying to get good at-bats."