Cornerback Nnamdi Asomugha knows he’s the target of much criticism, be it for his age or his disappointing play the past two seasons. But the 49ers’ newest acquisition has a ready answer for the critics.

“There’s a drive, there’s a hunger inside of me that says, ‘I know what I can do and I’m going to get it done,’ ” Asomugha said Wednesday in an exclusive interview with this news organization. “So, regardless of what others are saying or how others are feeling, I’m just going to make it happen.”

Asomugha, 31, was speaking for the first time since news of him agreeing to a one-year contract with the 49ers broke Tuesday. The former standout at Cal and with the Raiders, released by the Philadelphia Eagles last month, said he chose the 49ers over the New Orleans Saints. The contract includes no guaranteed money, according to ESPN, but carries a base salary of $1.35 million, with incentives worth an additional $1.65 million. Asomugha was due to earn $15 million from Philadelphia next season, $4 million guaranteed, after signing a five-year $60-million deal with the Eagles in 2011.

The 49ers intend to use Asomugha at cornerback, he said, even though he played safety for most of his college career and at times during his eight-year stint with the Raiders.

Despite his age and struggles in Philadelphia the last two seasons, Asomugha expressed zero doubt that he still has the ability to be the shutdown corner he was in Oakland, where he won Pro Bowl honors three times.

“I know what went wrong (in Philadelphia) and I know what I can do,” Asomugha said. “It’s not a see-what-happens-out-there sort of thing. For me, it’s going to happen. There isn’t a disbelief in me anywhere.”

In Oakland, Asomugha flourished in a scheme that favored man coverage and allowed him to use his long arms, physical style and sound technique. Although there has been some speculation that Asomugha wasn’t properly used in Philadelphia, Asomugha is taking a different view. He says the last two years will benefit him.

“I had a tough two years my first two in Oakland, and these two in Philly felt much longer than those two years,” Asomugha said. “But, having been through that before, I know that I’ve got what it takes to turn it around … and put a stamp on something like no one would have ever imagined. That’s a big reason why I’m here.”

The 49ers return starting cornerbacks Carlos Rogers and Tarell Brown, as well as nickel back Chris Culliver. Asomugha intends to win a starting job, but his primary focus is on helping the 49ers win a ring.

“From afar, you can tell they have the pieces in place and the game plan for winning,” Asomugha said. “Then, when you come up close and you talk to the coaches and the players, the front-office people, you realize how serious they are about it and how they’ve mapped it out. They made me a believer from the first time I met with them.”