HOUSTON -- Astros manager Brad Mills said he's still trying to get a firm grasp on what outfielder Justin Maxwell is capable of doing, considering he only had 273 career Major League at-bats entering Tuesday's game against the Cubs.

Mills has been turning to Maxwell to start against left-handers in recent days and had him batting third in the lineup against Cubs lefty Travis Wood. Maxwell has hit lefties better in his career (.240 vs. lefties, .174 vs. righties in nearly identical plate appearances), including a .364 batting average this season.

"We're kind of learning as we're going through things, and I don't want to put him in a box because he's got tons of ability and he plays well when he gets the opportunity," Mills said. "You want to give him the best opportunity to have that success."

The Astros claimed Maxwell of waivers from the Yankees on April 8, and he's made 11 starts for Houston. He stroked a go-ahead two-run homer in Saturday's come-from-behind win over the Rangers at Minute Maid Park.

"He definitely has some ability, and I think we've seen it," Mills said. "He can run a little bit, he's put together real well and he's got some strength. We need to get to see him play as we move along. It's probably been an injustice to him throughout his career that he hasn't gotten his opportunity to get 400, 500 at-bats, because that's how you get better."

Johnson recognizes kids for recycling efforts

HOUSTON -- Third baseman Chris Johnson, the Astros' Play Green ambassador, visited Landrum Middle School on Tuesday to recognize a class for its recycling efforts.

Johnson and Astros broadcaster Bill Brown read "William is Going Green" to Shannon Warren's sixth to eighth grade special needs class, which earned the recognition after Warren won a contest with an essay detailing her class's recycling projects.

"Those kids love it when we get to come in and take pictures and sign autographs," Johnson said. "Seeing the smiles on those kids' faces makes my day, so it was awesome."

The class was also recognized before Tuesday's game against the Cubs at Minute Maid Park.

The book emphasizes the importance of recycling in keeping a healthy environment. It also details the importance of the little things, like donating old toys or turning off the lights when they aren't needed.

Johnson has been the Astros' Play Green ambassador for a couple years now and does two or three school visits a year.

"It's not one of those paid deals that you do," Johnson said. "This is strictly [volunteering] that I do. It's something cool to go out every once in a while and see the kids. It makes it worth it to see the smiles on their faces."

Mills continues to tinker with different lineups

HOUSTON -- Through the first 43 games of the season, manager Brad Mills has used 35 different lineups. The last time Mills used the same lineup on back-to-back days was April 22-23.

The fact that Mills uses both of his catchers, Jason Castro and Chris Snyder, contributes to the high number of unique lineups, but Mills said Tuesday that he's adjusting the lineup frequently as his younger hitters reveal their tendencies.

"We'd like to have one lineup, and that'd be it, if we had our choice," Mills said. "There's no doubt."

Tuesday's lineup was one of the most unique of the season. Left fielder J.D. Martinez batted fifth for the first time this season and center fielder Jordan Schafer, returning from a lower leg muscle strain, made his first start in the eight-hole. Right fielder Justin Maxwell batted third for the second time this season.

Mills said the lineup could continue to change throughout the season, depending on how guys swing the bat or what tendencies they show.

"You go through Spring Training and you see one thing, and as you start the season, you go on top of that," Mills said. "You want to try to take care of guys and put them in positions to give them the best chance of success, plus help the ballclub."