CLEARWATER, Fla. -- With the 25-man roster needing to be set by Thursday night, the Astros are going to be closely monitoring the ailing back of catcher J.R. Towles.

Towles has missed a couple of games because of tightness in his back, but he took 25 swings off the tee on Monday in Kissimmee, Fla., and said he felt OK, according to manager Brad Mills. If he's healthy, Towles is likely to join Humberto Quintero on the Opening Day roster.

"It was good to see him do some baseball activity," Mills said. "He played catch and threw. He still felt it in his back, but he felt much better. To have him go out there and do some baseball activity is huge."

Mills said it's too early to tell how Towles' back injury would affect the roster.

"We'll see how he is [Tuesday] for the flight to Oklahoma City, and we'll go from there," he said.

Mills anoints Wallace starter at first

CLEARWATER, Fla. -- Brett Wallace did everything he could this spring to establish himself as a starter, and manager Brad Mills confirmed Monday he would indeed be at first base for the Astros when the regular season begins.

Wallace entered Monday's game tied for the Grapefruit League lead with 18 RBIs and tied for second with 23 hits. The Astros were prepared to move Carlos Lee to first if Wallace struggled at the plate this spring.

"He's done a good job both defensively and offensively this spring," manager Brad Mills said. "He came in and worked hard over the winter. He came straight into Spring Training swinging the bat extremely well, and he's kept doing it all the way through."

Mills told Wallace, whom the Astros acquired in a trade with the Blue Jays in July, on Saturday the job was his. Wallace said he knew he had put himself in great position by the way he swung the bat, but it was nice to hear it was official.

"My goal this spring was to come in and be in good shape and play my game, and be comfortable with my surroundings and my teammates and the organization and play hard and play aggressively," he said. "That's what I was able to do, and by doing that, I hopefully showed them I could help the team win."

Wallace said he didn't feel any pressure.

"I became real close to this group of guys," he said. "From C.J. [Chris Johnson] and [Jason] Castro and Hunter [Pence] and even Carlos [Lee] and J-Mike [Jason Michaels], I was just having fun with them, and they knew where I was and that I was ready to play. Having those relationships helped loosen me up and have fun."

Inglett eager for new opportunity with Astros

CLEARWATER, Fla. -- Joe Inglett, acquired in a trade with the Tampa Bay Rays on Sunday, joined his new Astros teammates on Monday for the final Grapefruit League game of the season against the Phillies. He was in the starting lineup at designated hitter.

"It's been a roller-coaster ride," he said. "This offseason was a roller-coast ride and now this is a roller-coaster ride. It's for the better. It's an opportunity, and that's all you can ask for."

Inglett is technically a non-roster player, but it appears he's got a good chance to make the club in a backup role, especially considering he flourished in that role last year with the Brewers and can play the infield, as well as some outfield. It also helps that he hits left-handed, which was a need for Houston.

Last year, Inglett led all Major league players in pinch-hits, batting .294 (20-for-68) with two doubles, four triples, a home run -- which came against the Astros -- and six RBIs. He hit .254 with eight doubles, five triples and eight RBIs in 102 games.

"It was my first time ever kind of being in that situation, and it was nice to have a guy named Craig Counsell in my corner," Inglett said. "I pretty much shadowed him. He taught me how to be a pro and how to be pretty much a threat off the bench."

The Astros are still trying to identify a starting shortstop in the wake of the Clint Barmes hand injury, with Angel Sanchez and Tommy Manzella the likely candidates. Inglett, Matt Downs and Anderson Hernandez are vying for the two backup infield spots. Sanchez is out of options.

Worth noting

Right-hander Cesar Carrillo, who was outrighted by the Astros earlier this spring, will start against the Astros for Triple-A Oklahoma City in Tuesday's exhibition game in Oklahoma City. ... Right-hander Alberto Arias, who's missed the entire spring with shoulder tendinitis, threw a bullpen session on Monday in Philadelphia.