SANTA CLARA -- Cornerback Tarell Brown participated in the 49ers' first practice of training camp Thursday, only hours after learning he's lost $2 million in potential salary for failing to participate in the team's offseason program.

"It definitely was hard to concentrate just because my mind was somewhere else," Brown said after practice. "But this is a business and I have a job to do, and the 49ers are paying me to do a job.

"I have to come out here regardless of what's happening off the field."

Brown blamed the financial fiasco on the oversight of his now-former agent Brian Overstreet, and the starting right cornerback only learned of it Thursday morning on Twitter. Yahoo! Sports broke the story.

"When you ask somebody that advises you to do certain things, and not knowing a clause in your contract, you put too much trust into people," Brown added. "That's what happened in this situation."

Brown is now slated to earn $925,000 salary in the final year of his current contract. Overstreet did not return a phone message seeking comment.

Rather than participate in the nine-week program from April to June, Brown instead chose to train in Dallas with his longtime trainer, former Olympic sprinter Jon Drummond.

"It's something I've always done as far as (spending) the offseason at home, getting in shape," Brown said. "It had nothing to do with not being in shape, not wanting to work out, no contract problems or anything like that."

Brown did, however, participate in the 49ers' 2012 offseason program, and he responded by playing arguably the best among the 49ers' cornerbacks last season en route to the Super Bowl. He had only two interceptions in the regular season, but he made one in the playoff opener against Green Bay and forced a key fumble during the 49ers' second-half comeback bid in their Super Bowl defeat to Baltimore.

Brown lined up in his familiar spot at right cornerback with the 49ers' other defensive players during Thursday's practice, and he made a nice play to deflect a third-down pass attempt by Colin Kaepernick.

The 49ers still could extend Brown's contract, or he could hope to recoup some of that lost $2 million once he hits free agency next spring. Brown is one of 23 players on the 49ers' roster who don't have contracts for next season.