HOUSTON -- A day after a hard collision at first base with Brewers slugger Prince Fielder, Astros first baseman Brett Wallace was held out of the lineup on Saturday as a precaution. Wallace was available to play against the Brewers and is expected to return to the starting lineup for Sunday's series finale.

"I feel pretty good," Wallace said. "I came in and got some treatment and I was able to go down the cage and hit and took [batting practice] and moved around pretty good. I'm feeling pretty good. I'll hopefully be back in there tomorrow."

Wallace was relieved the injury hadn't worsened when he woke up Saturday morning.

"I think last night they were worried it was going to swell up a lot more and get tighter and tighter," he said. "I got up and I was actually pretty loose and able to get around most of the day and get the treatment in. It's still stiff and a little sore, but definitely playable."

Manager Brad Mills said Wallace was available to pinch-hit as long as he had time to warm up. "The situation is with a night game [Saturday] and a day game [Sunday], if he played tonight he would probably have to sit out tomorrow," he said. "If he gets one of those two days, I would probably give him the day [off] today and give him the chance to heal and feel better and heal. He has an afternoon game tomorrow and then into Monday night to heal as well."

Figueroa moves to 'pen; Aneury to rotation

HOUSTON -- Astros manager Brad Mills announced Saturday that he was moving right-hander Nelson Figueroa to the bullpen and replacing him in the starting rotation with rookie Aneury Rodriguez, who made 131 starts in the Minor Leagues from 2005-2010 in the Rays organization.

"It's a dual move to help strengthen our bullpen a little bit because Figgy's so valuable because he can do everything -- short [relief], long, middle, whatever we need," Mills said. "And I think that's another experienced arm that we're going to be able to put down there, and he's active for tonight."

Rodriguez, acquired by the Astros in the Rule 5 Draft last December, will make his first career Major League start Tuesday in Cincinnati against the Reds. He's appeared in nine games in relief this year, posting a 6.57 ERA in only eight innings.

"I'm excited because I was a starter for five years and I like it better because I have more time for preparation," said Rodriguez, who could throw as many as 80 pitches.

Figueroa, who is 0-3 with an 8.28 ERA in five starts, will bring the ability to pitch in long relief, as well as giving the young relief corps a veteran presence.

"I'm excited," Figueroa said. "It's another opportunity to help out the team. Whatever I can do, I felt like I did a very good job of that last year, helping out the 'pen. The 'pen's been kind of stretched out. We're thin right now and some guys have been in there multiple games. It will be good to lend a hand out there, and hopefully I can get back in the groove."

Sanchez bats third, Lee fifth in lineup shuffle

HOUSTON -- With first baseman Brett Wallace still nursing a sore hip from his Friday collision with Brewers slugger Prince Fielder, and feeling a need to get more speed at the top of the order, Astros manager Brad Mills stirred up his lineup for Saturday's game against Milwaukee.

Carlos Lee, who has hit fourth all season and has struggled this year, was moved down to fifth and played first base.

Jason Bourgeois batted second and played left field, and Angel Sanchez returned to the lineup, making his first start at second base and batting third. Hunter Pence was moved into the fourth spot in the lineup. Clint Barmes, who batted second in his season debut on Friday, hit eighth.

"The whole thought is Bill Hall's got the day [off] and we're trying to get Sanchez back in there," Mills said. "He's swinging the bat really well for us, and this way we get some speed and some guys that are getting on base in front of Hunter and Carlos. It is new, but I don't know how we're going to use this going forward."

Mills said Lee's struggles weren't a driving factor in the lineup shuffle. Lee is a career .281 hitter with 39 homers and 196 RBIs in 321 games in the fifth spot, including 12 games last year (.265 average).

Lee entered Saturday hitting .200 with two homers and 15 RBIs.

"I went back and looked at his numbers last year from April 30, and he had five RBIs last year and he has 15 now," Mills said. "He was hitting 20 points higher than he is now with one home run and he has two. He's still driving some runs in for us compared to last year."

Lopez could return from DL on Monday

HOUSTON -- Astros right-hander Wilton Lopez could be activated as early as Monday after throwing a simulated game Saturday without any complications. He's been on the disabled list with a right elbow ulnar nerve irritation.

Lopez threw close to 30 pitches and faced two hitters, a left-hander and a right-hander, in an effort to simulate his usual one-inning role.

"He threw the ball really well," Astros manager Brad Mills said. "He's probably on target in the next few days to be able to be active. We'll see how he is after the icing and treatment and everything, but there's not reason to believe he won't be ready to go."

Lopez emerged as the Astros' setup man last year, going 5-2 with a 2.96 ERA in 68 appearances. Mills is hoping that once Lopez is healthy, he can recapture the stuff the showed last year.

"We know that the ball wasn't coming out of his hand quite as good [when bothered by the elbow injury], but we do know now after watching today, that he looked pretty nice," Mills said. "He looked really good with the ball coming out of his hand."