HOUSTON -- Jason Castro took batting practice on the field for the first time before Monday's game against the Nationals and said there's still a chance he will return before season's end.

"I definitely still have a little bit to go," Castro said. "Hitting, I feel pretty good right now. I'm still working on easing into squatting a little bit, and my running's coming along pretty good. I've got some time still to go, but I can tell I'm getting closer with stuff like this today."

Castro, who hasn't played in a regular-season game after tearing ligaments in his right knee, will go to Florida within the next few days to continue rehab.

"It's our Spring Training site, and they have some staff down there," he said. "That way, when the team's on the road, I can still get my work in every day."

Castro said that hitting on the field is a milestone in his recovery process.

"You take things like this and you use them to kind of help push you through the tougher parts," he said. "Any time I can do something like this and really experience the progress I've made, it's real positive."

Wright feels more prepared thanks to tweaks

HOUSTON -- Reliever Wesley Wright has made a few tweaks in his delivery and feels more prepared as he joins the Astros for the first time since September 2010.

"I think I've been around long enough to understand how things work here," Wright said. "You just take it one day at a time, and you just never know what tomorrow might bring. Things happen, people get injured, whatever it might be, and you end up staying longer than you thought."

Wright said that although the mechanical differences on the mound aren't drastic, they have aided his recent success. He is 2-1 with a 2.63 ERA in 29 appearances at Triple-A Oklahoma City.

"I just lowered my leg kick a little bit to try to stay on line a lot longer, and it allows me to get the ball out front a little bit better and keep the ball down in the zone," he said.

Matt Downs is out for the next three games on paternity leave, giving Wright the opportunity to join the club.

"It's good to be back," Wright said. "It's been a while since I was here, and I just want to get back and be able to contribute in the best way I possibly can and just enjoy being here, whether it's three days, a week or whatever it might be."

Mills sits Wallace for opener with Nats

HOUSTON -- Brett Wallace was not in the starting lineup on Monday night even though the Astros faced a right-hander in the Nationals' Jason Marquis.

Manager Brad Mills decided to put Jason Michaels in left field and Carlos Lee at first base because of their past success against Marquis.

Michaels was hitting 7-for-10 with a home run, a double and four RBIs against Marquis in his career entering the game, and Lee was hitting .400 with four homers and 12 RBIs in 40 at-bats.

"With Carlos ... and Jason Michaels swinging the bat very well against this guy, I just thought it would be a good time to make sure they get in the order," Mills said before the game. "We're going to face a couple of lefties on [our next] road trip, but it's a long road trip, and I just wanted to get them in the lineup."

The move paid off. Michaels scored the game-tying run in the fifth inning on an RBI double by Carlos Corporan, and Lee gave the Astros a one-run lead the following inning on an RBI double to left field, scoring Angel Sanchez from first base.

Mills talked to Wallace after Sunday's game to tell him the news.

"I said, 'You had two hits last night, and the approach that you've been having at the plate the last three, four days is much better, and I want you to stay with that,'" Mills said. "'This is nothing against you at all.'"

Worth noting

• The Astros have signed 29th-round Draft pick Wallace Gonzalez and non-drafted free agent C.C. Yavapi. Gonzalez is an outfielder from Bishop Amat High School, and Yavapi is a right-handed pitcher.

• Jason Bourgeois, who has been on a rehab assignment with Double-A Corpus Christi, is scheduled to join Triple-A Oklahoma City on Tuesday.

• Monday night marked the first time the Astros and the Nationals have met this season.