There are plenty of questions hanging over the 49ers secondary this offseason.Will safety Donte Whitner, an unrestricted free agent, walk away? Will the team try to re-sign cornerback Tarell Brown, a starter for the past three years who was supplanted because of an injury late this past season? And will the 49ers keep starting corner Carlos Rogers, who is due to receive $6.6 million in 2014?Much will be determined from February through May, with free agency and the draft.But one given is the return of cornerback Chris Culliver.Culliver was the 49ers' nickel corner in 2012 and played a large role on a defense that helped San Francisco reach the Super Bowl.But Culliver blew out his ACL early in training camp last August and missed the entire 2013 season. The 49ers shuttled several players in and out of the nickel role in his absence, including Tramaine Brock – who eventually won a starting role – Nnamdi Asomugha, Brown, Eric Wright and Perrish Cox. With Asomugha released during the season and Brown, Wright and Cox all entering free agency, the cornerback position could be the biggest area of change for the team this year.But Culliver's rehab from surgery has gone well,...