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09/02/09 6:46 PM ET

Giants bring up top prospect Posey

Fifth overall pick in '08 Draft added for catching depth

PHILADELPHIA -- Buster Posey's speedy ascent to the Major Leagues reflects the Giants' concern about their injury-afflicted catching corps, manager Bruce Bochy said Wednesday.

Bengie Molina, the Giants' No. 1 catcher, entertained the notion that management might be telling him that while he's needed, he isn't necessary, to borrow a saying from legendary football coach Paul Brown.

Posey, who received a franchise-record $6.2 million bonus after the Giants selected him in the first round (fifth overall) of last year's First-Year Player Draft, wasn't expected to be brought to the Majors from Triple-A Fresno after rosters expanded to 40 players Monday.

But Molina's tight right quadriceps, which kept him out of the lineup for the eighth game in a row Wednesday, largely prompted the Giants to purchase Posey's contract. Bochy explained that he didn't want to be placed in a predicament where Molina and reserve Eli Whiteside might be unavailable due to injury or removal for a pinch-hitter or pinch-runner. That would force Bochy to use Ryan Garko, who's considered an emergency catcher, or Pablo Sandoval, who's striving to overcome a right calf injury, behind the plate. Either alternative would be risky for a contending club such as the Giants, who began the day trailing National League Wild Card leader Colorado by one game.

Summoning Posey thus represented San Francisco's most logical solution for catching insurance, Bochy said.

"Buster's the best catcher in our system," Bochy said. "We needed some help. We felt at this time this would give us more coverage, a little more depth."

Bochy added that he wouldn't hesitate to use Posey during the late innings -- which is a very real possibility, given the Giants' tendency to pinch-run for Molina at that juncture. Molina said he plans to start Thursday's series finale vs. the Phillies.

Posey, who hit .325 with 31 doubles, 18 home runs and 80 RBIs in 115 games with Class A San Jose and Fresno, called himself "extremely excited" to join the Giants, who also purchased the contract of left-handed reliever Dan Runzler from Triple-A.

"I'm even more happy to be on a team fighting for a playoff spot," said Posey, 22. "I'm looking forward to the atmosphere."

The atmosphere around the Giants might have grown a little noxious for Molina, who is eligible for free agency after this season and has wondered whether the club wants to retain him. Despite Bochy's explanation for Posey's promotion, Molina sensed that the future is being dangled in front of him.

Asked if he believed that club management was sending him a "message," Molina replied, "You know what? Probably. This is baseball, and as they can tell you, it's a business. This might mean that I might not be coming back next year. Who knows? I'm ready for everything, man. I've been in the league so long. I know how baseball goes."

Molina added, "The only thing that I can say is that I have my chin up, always. I've done enough for this club for the past two, three years. I've helped many guys. I hold my ground. I don't have anything to be ashamed of."

Neither does Posey. After he earned California League Mid-Season All-Star honors by hitting .326 with 23 doubles, 13 homers and 58 RBIs in 80 games with San Jose, the right-handed batter hit .222 in his first 14 games at Fresno. But Posey adjusted, recording a .380 average in his last 21 games with the Grizzlies.

"When you struggle, you're going to be a little discouraged," said the 6-foot-1, 205-pound Posey, who was briefly sidelined after enduring a home-plate collision in early August with New Orleans' John Lindsey. "But I never felt like I was overmatched, necessarily."

To clear room for Posey and Runzler on the 40-man roster, right-hander Ryan Sadowski and left-hander Jesse English were designated for assignment.

Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.