HOUSTON -- It's been more than a year since Ryan Theriot's last home run. It just seems that long between wins for Carlos Silva.

Theriot hit his first home run in 700 at-bats, a solo shot, and Geovany Soto added a two-run double to back Silva and lift the Cubs to a 5-2 victory Monday night over the Astros.

Silva (10-4) reached double-digit victories for the first time since 2007, when he won 13 games with the Twins, and has a chance at matching his personal high of 14. What if you had told manager Lou Piniella that he'd get 10 wins from Silva, acquired from the Mariners for Milton Bradley?

"We would've been very pleased," Piniella said. "When [general manager] Jim [Hendry] made that deal with Seattle, if he could've written a '10' by Carlos, he would've been very pleased.

"Now he has a chance to put a few more on the board," Piniella said. "He's done a real nice job here. He's a professional and he's throwing more pitches because he's getting deeper in counts. What is he, 10-4? I think Jim would've done cartwheels."

The right-hander began his first season with the Cubs 8-0, but he couldn't get past the second inning in his last two starts. He was given an extra day to work on the side with pitching coach Larry Rothschild, who got the right-hander to tweak his mechanics and have a more compact delivery. It worked.

"What an improvement over his last start," Piniella said.

That last start also was against the Astros, when Silva gave up five runs on seven hits in one inning. On Monday, Silva held Houston to one run on five hits over five innings, and the run came in the first on Lance Berkman's RBI single.

"He kept mixing his pitches," Cubs catcher Geovany Soto said. "We tried to mix pitches up and keep them guessing. With this team, they come out swinging and you have to do a little twitch here and there."

Silva isn't counting his wins yet. The season isn't over.

"With this offense we have and the pitching staff we have, we can do some damage," Silva said. "I was a little sad -- right when the team was playing so good, I had these two bad games."

Silva wasn't concerned about his two previous starts.

"I had a bad year last year, and this year I'm having a pretty good year so far," he said. "If you don't learn from those [bad games] -- I'm a guy who trusts God. If I'm going to get frustrated over the last two games, if those two are going to take me out of the year I'm having, then I'm very poor [mentally].

"I'm not concerned at all. We're human and have bad games. The only thing I can do is keep working."

The Cubs now are 19-28 against National League Central teams, including a 4-6 mark against the Astros, and have won eight of their last 13 games.

Soto got things started when he hit a two-run double in the second off Wesley Wright (0-1), driving in Marlon Byrd, who had walked, and Alfonso Soriano, who doubled. The Cubs added on in the third, as Derrek Lee doubled and moved up on Aramis Ramirez's single. Lee scored on Byrd's fielder's choice, forcing Ramirez at second, and Soriano followed with an RBI double.

"I was happy with the way I competed," Wright said. "They have a solid lineup over there, one through eight. More than anything, I was impressed with how they hit with runners in scoring position. They took advantage of it all night long, and when they do that, it's going to be tough to beat them."

The Cubs may be a man short. Soto had to leave the game after six innings with a bruised left foot, injured when he fouled a pitch off it in the third. His status was day-to-day.

Theriot connected on a 1-2 pitch from Nelson Figueroa, who started the sixth, for his first home run since June 29, 2009, when he delivered against Pittsburgh's Zach Duke. The infielder now has 15 career homers, and his homerless stretch was the longest active streak in the Major Leagues.

Theriot's teammates gave him the silent treatment when he got back into the dugout.

"I knew it was coming when I was coming around third base," Theriot said. "It's not funny. I'm going to initiate the silent treatment for every homer from here on out."

Maybe his ball got a boost from a jet stream?

"The wind was blowing out here, and I was able to get it up in the wind," he said.

Yes, the roof was closed Monday at Minute Maid Park.

Angel Sanchez singled with two outs in the Astros' seventh off Justin Berg, and moved up because of some confusion by the Cubs. Berkman hit the ball to Lee, and the first baseman looked at second, but rookie Starlin Castro wasn't covering, so Lee threw to Berg at first but too late. Everyone was safe, and Hunter Pence followed with an RBI single.

"These are the things [Castro] has got to learn," Piniella said of the 20-year-old. "It should be an easy play for him, because Berkman is up and he's playing him up the middle. The ball Derrek catches, his momentum is going to second base. He makes a little throw to second and the shortstop covers and the inning is over.

"Those are growing pains. [Infield coach Alan Trammell] is earning his money."