HOUSTON -- Being 15 games over .500 and holding a 3½-game lead in the NL West wasn't enough for San Francisco Giants general manager Brian Sabean.

The architect of San Francisco's stirring run to its first World Series title since 1954, Sabean is once again shaking up his roster.

With infielders Freddy Sanchez and Miguel Tejada on the disabled list, the Giants acquired second baseman Jeff Keppinger from the struggling Houston Astros for two Double-A pitchers on Tuesday.

San Francisco also called up Brandon Belt from Triple-A Fresno to relieve first baseman Aubrey Huff, who has tightness in his lower back.

Sabean hasn't ruled out additional moves, either.

"Without being harsh, this group just isn't getting it done," the GM said before San Francisco hosted the Los Angeles Dodgers. "We need to somehow extend the lineup any way we can, and we think this is an upgrade."

The Giants have had numerous injury problems in their infield this season. Sanchez is out indefinitely with a dislocated right shoulder and Tejada was placed on the disabled list Tuesday with an injury to his lower abdomen. San Francisco signed former Houston second baseman Bill Hall after Sanchez was injured, but Hall is on the DL because of a leg laceration.

Tejada, who has played primarily shortstop and third base, left Monday's 5-0 win against the Dodgers after straining his lower abdomen while trying to field a grounder in the third inning.

"We felt with the injuries we've had up the middle, (Keppinger is) going to give us some strength there, some versatility," Giants manager Bruce Bochy said. "We needed some help there and Brian did a terrific job getting us a really nice player to help out."

The 30-year-old Keppinger arrived in Houston in a March 2009 trade from the Cincinnati Reds. He is a career .284 hitter with 30 homers and 200 RBIs with the New York Mets, Kansas City Royals, Reds and Astros since his debut in 2004.

Keppinger, batting .307 with four homers and 20 RBIs in 43 games this season since his return from foot surgery, is looking forward to playing for a team in the playoff hunt. He's expected to bat in the No. 2 spot in San Francisco's order.

"I get to go to a team that's in contention," Keppinger said. "This will be the first time I've ever actually been on a team that's been in first place or even with a winning record. It's definitely exciting and that's what you want when you play this game."

Sanchez, sidelined since June 10, was transferred to the 60-day DL to make roster room for Keppinger.

The trade for Keppinger is reminiscent of the moves Sabean made in 2010 when he signed Pat Burrell to a minor league contract, traded for reliever Javier Lopez and picked up Cody Ross off waivers from the Florida Marlins.

All three played key roles in the Giants' championship run, something Sabean hopes to re-create this year.

Reports continue to circulate that San Francisco will make a run at Mets outfielder Carlos Beltran, and Sabean hinted he was working on a "bigger deal" last week before turning his attention to Keppinger.

While trading for a potential free agent such as Beltran would likely cost the Giants one or two of their top prospects in a short-term fix, Sabean didn't rule it out.

"Quite frankly we're very lucky, and we know it, to be 15 games above .500," he said. "There's a lot of baseball left to be played, so it's all going to be a function of how much money we can take on, the fallout prospect-wise and whether ideally we're going to deal with a rental or not."

The last-place Astros received right-handed starter Henry Sosa and right-hander reliever Jason Stoffel from the Giants.

"You don't like to see a guy like Keppinger go," Houston manager Brad Mills said. "He's such a professional hitter. I'm sorry to see him go, but I'm happy for him. It's an exciting time, I think, for the organization. We got a couple good arms, it sounds like -- not just looking at their numbers, but the reports on them as well. The two guys we got look to be pretty solid players."

Houston also purchased the contract of infielder Jose Altuve from Double-A Corpus Christi, and Mills said he will get significant playing time at second base.

The 25-year-old Sosa spent time at Triple-A Fresno this season but is currently at Double-A Richmond. He is a combined 8-3 with a 5.51 ERA in 63 2/3 innings.

Stoffel has 13 saves and a 3.98 ERA in 32 games with Richmond this season. He is 4-6 with 42 saves and a 3.77 ERA in 101 career minor league relief appearances.

Houston general manager Ed Wade said he thinks Sosa could become a part of the Astros' rotation as early as next season.

"I think as we move forward here, if we have an opportunity to add prospect depth to the system, we're going to do that," Wade said. "It's about trying to build quality within to get to a point where we can have that core nucleus be developed from within our own organization. That's a very important aspect of what we're trying to do here."

Wade didn't enjoy trading Keppinger but felt the move was best for his last-place team.

"We've got some infield depth and it gives us a chance to get Altuve up here and let him get his feet wet at the big league level," Wade said. "At the same time add the pitching depth that we're going to desperately need going forward."

The 21-year-old Altuve has a combined .389 average at Class A Lancaster and Corpus Christi this season. He has 22 doubles, 10 homers and 59 RBIs with 24 stolen bases. Mills said Altuve will start at second base on Wednesday.