As a rule, unrestricted free agents are harder for NFL teams to retain than restricted free agents.
The question with Browner was whether or not he gets credit for an accrued season in 2005, when he spent the year on injured reserve with the Broncos. Without that season, 2013 would be Browner's third in the NFL, one short of qualifying for unrestricted free agency under the NFL's collective bargaining agreement. But Sando – citing team, league and NFL Players Association sources – reports that Browner gets credit for that 2005 season, meaning he'll have four accrued NFL seasons after 2013 and can therefore become a UFA.
It's an important distinction to make, mainly because Browner's status as a UFA will complicate the Seahawks' efforts to retain him should they wait until next offseason. Any team signing another team's RFA has to relinquish a draft pick and is only guaranteed one year of service from that player, which is part of the reason why RFAs rarely change teams. There are no such guidelines with UFAs, making it easier for those free agents to sign elsewhere.
This could all be a moot point if the Seahawks decide to sign Browner to an extension before the end of next year. If they don't, they could be at a crossroads with Browner and their other starting cornerback, Richard Sherman, who will be eligible for an extension having completed his third NFL season.