Cornerback Nnamdi Asomugha said Wednesday that he has something to prove every season. OK, the newest member of the 49ers fessed up, maybe more so this year.

"My mind-set is to come in and compete and be the best I can possibly be," said Asomugha, who signed a one-year deal worth up to $3 million earlier in the day. "I've had a chip on my shoulder every year that I've played. I think it's bigger this year."

Asomugha, 32 in July, is coming off two rocky seasons and being cut by the Eagles, and he knows why things didn't work out. Not that he is going to tell you.

"I'm not the type of person who lists ... that all starts to sound like excuses to me," he said. "The bottom line is it didn't work out. I tried my hardest for it to work out. I believed all the way up until the end that it was going to work out."

Asomugha is not taking any guaranteed money in the deal, and can make $1.65 million in incentives on top of his $1.3 million salary. The 49ers have nothing to lose in the deal, and a Pro Bowl-caliber cornerback (from his days with the Raiders) to gain.

"We are very pleased to add Nnamdi to our defense," 49ers general manager Trent Baalke said. "Throughout his career, Nnamdi has accomplished a great deal on the field and in the community. We look forward to his contributions to our team and the Bay Area."