Cards' Carpenter headed for Double-A

On the shelf

■ Astros ace Roy Oswalt was placed on the 15-day disabled list Saturday with a strained hip and a herniated disk in his back. Manager Cecil Cooper said Oswalt (7-8) should be ready to start again on July 28 for the opener of a three-game series with Cincinnati. Oswalt injured his hip in his June 30 start against Los Angeles. He re-aggravated the injury in his next start on July 11, leaving the game after throwing only 17 pitches against Washington.

Daric Barton smacked his head on the bottom of a pool during the All-Star break, requiring six staples to close the gash and leaving the Oakland first baseman with a neck strain that landed him on the disabled list Saturday. Barton was placed on the 15-day DL, retroactive to July 14.

On the move

■ The Orioles addressed their shaky shortstop situation by acquiring Juan Castro from the Rockies in a trade of minor-league infielders on Saturday. Castro was batting .300 in 18 games with Triple-A Colorado Springs. The former Red has more than 11 years of major-league experience.

Short hops

David Ortiz homered for the third straight game during a rehabilitation assignment with Triple-A Pawtucket on Saturday night. The Red Sox slugger is expected to return to the majors for the home series with the Yankees on July 25.

■ Yankees outfielder Johnny Damon (sprained left shoulder) took batting practice with his teammates on the field and hopes to come off the disabled list Sunday.

■ The Mets decided that Pedro Martinez won't pitch during a three-game series against the Phillies that starts on Tuesday. Martinez strained his groin while running the bases on July 7. Five days later, he left his start against Colorado after only four innings because of tightness in his shoulder.

On the mound

■ Two of the hottest pitchers in the National League face off Sunday when Tim Lincecum's Giants host Manny Parra and the Brewers. Lincecum (11-2) leads the majors in strikeouts, while Parra (8-2) hasn't lost a game in his last 13 starts.

Cardinals ace Chris Carpenter, sidelined since opening day in 2007 because of an elbow injury, will begin a rehab assignment on Sunday with hopes of joining the rotation in August.

Carpenter, the 2005 NL Cy Young winner, will begin his rehab stint with Double-A Springfield. The team is hopeful he won't need the full month before joining the staff and anticipate him joining the rotation immediately, rather than working out of the bullpen at first.

While the final stage in Carpenter's climb back from reconstructive surgery begins, the team is prescribing two weeks of rest for rehabbing left-hander Mark Mulder.

Mulder had his twice surgically-repaired shoulder examined by a handful of doctors during the week. The team said Saturday the situation would be re-evaluated after the rest period.

The former 20-game winner came off the disabled list on June 27 but returned to it on July 10.