HOUSTON -- Ryan Theriot is the Cubs' new leadoff man, at least until Alfonso Soriano gets back.

Theriot batted leadoff for the 14th time this season Monday night when the Cubs opened a three-game series and seven-game road trip at Houston. Soriano will be out at least one month with a strained right quad, which he injured Sunday night.

"I just keep my same approach," said Theriot, who has hit .305 batting first this season. "I just don't have the luxury of having [Soriano] on second base. You keep the same approach. I've said this before, you're only the leadoff batter once. I've hit in that spot plenty in the past to feel comfortable."

Cubs manager Lou Piniella said he will likely keep Theriot in the No. 1 spot but will mix and match with the outfield. Eric Patterson was called up from Triple-A Iowa on Monday and may start Tuesday in left field. On Monday, Matt Murton was in left, Angel Pagan in center and Mark DeRosa in right against lefty Wandy Rodriguez. Against right-handers, Patterson could start in left, Jacque Jones in center and Cliff Floyd in right.

"When you lose such a big part of your ballclub, a lot of people have to step up," Theriot said.

The addition of Patterson gives the Cubs more speed, and they are definitely younger.

"We can do different things," Piniella said. "I'm just not exactly sure what right now. Let's see it for a few days."

Welcome: Patterson, the younger brother of former Cubs outfielder Corey Patterson, was excited about being called up for the first time.

"It's something you work on ever since you start playing baseball, to get here and to be in a situation and in a pennant race and try to do what you can to help these guys win baseball games," Patterson said. "It's still kind of sinking in. It's definitely something I've been looking forward to for awhile."

He was dozing on the floor of his living room Sunday night when Iowa manager Buddy Bailey called with the news. Roommate Buck Coats had the couch.

And big brother Corey?

"He was thrilled," Eric said. "He said, 'Congratulations. Don't change a thing. Just keep going.'"

Patterson, 24, was batting .299 with 23 doubles, six triples, 14 homers and 62 RBIs in 111 games for Iowa. Named to the Pacific Coast League All-Star team, he has played second, left and center this year.

The Pattersons are the 10th set of brothers to play for the Cubs. Eric knows he'll be compared to Corey, who now plays for Baltimore.

"It comes with the territory," he said. "It's not new to me. It's been happening all my life. I'm my own player, and he's his own player."

The Cubs did consider recalling outfielder Felix Pie, who had been with the big-league team earlier. Cubs general manager Jim Hendry consulted with the Iowa coaching staff as well as the roving Minor League coaches.

"We're trying to bring up the guys who are hot and can fill the need we have," Hendry said. "If we need somebody for pure defense, it would be Felix. We kicked it around a lot of different ways, but in the end, you listen to your people. There were no negatives about Felix."

Happy trails: The Cubs also released pitcher Wade Miller on Monday. The right-hander was 0-1 with a 10.54 ERA in three starts for the Cubs before he was placed on the disabled list in April with back spasms.

"He's a good guy," Piniella said of the 30-year-old right-hander. "It's a shame that I didn't get to manage him when he was healthy and throwing the ball when he was pitching well. He's a competitive guy, and he's a good teammate. The whole time he was here, he was rooting for the players and for the team.

"He worked hard. It's a darn shame his arm didn't come back and didn't respond to the work he put in. Maybe some rest over the summer and the winter, and it'll happen for him. I hope it does, because he's a good guy."

Miller began his career in 1999 with the Houston Astros, and has a 62-46 career record and 4.10 ERA in 151 games (147 starts).

Extra bases: The Cubs are considering the possibility of someone in the Minor Leagues making a spot start to give the other starters a breather. ... Kerry Wood passed all the tests on Monday. "We'll use him as we need him," Piniella said. ... Sean Marshall has new contacts and said his right eye is better. He had a scratched cornea, although that wasn't the reason for his struggles in his last start. ... The Cubs also designated infielder Brian Dopirak for assignment. Dopirak, 23, was batting .259 with 16 home runs and 54 RBIs between Class A Daytona and Double-A Tennessee.

Minor matters: J.R. Mathes gave up four runs on 10 hits over five innings in Iowa's 9-8 win over Las Vegas on Sunday. Geovany Soto hit his 19th homer, a two-run shot. ... Ryan O'Malley gave up seven runs on seven hits over four innings in Tennessee's 11-8 loss to Montgomery. ... Paul Schappert gave up three runs on six hits over five innings in Daytona's 5-4, 12-inning loss to Fort Myers. ... Jake Renshaw gave up four runs on eight hits over five innings in Class A Peoria's 12-4 loss to Lansing.

On deck: Marshall will start the second of this three-game series against Woody Williams and the Astros on Tuesday. First pitch is scheduled for 7:05 p.m. CT, and the game will be broadcast on Comcast Sports Net.