When the 49ers open training camp this month, the most solid unit on the entire roster will the starting offensive line.Tackles Joe Staley and Anthony Davis, guards Mike Iupati and Alex Boone and center Jonathan Goodwin started every game of the 2012 season together and formed one of the best – if not the best – fivesomes in the NFL.Going forward, however, 2013 could be the last together for the fab five.Staley and Davis aren't going anywhere, and neither are Iupati and Boone. But Goodwin – the veteran who helped the New Orleans Saints win a Super Bowl and aided the Niners in winning another one – is entering the final season of his contract in San Francisco.At age 34, Goodwin renegotiated the final year of his deal in May to give the team more salary cap space. The reworked deal reduced his salary for this season from $3.7 million to $2.5 million, with the team giving him $1 million guaranteed in exchange for the change.The Niners signed Goodwin in August of 2011 to a three-year deal, and Goodwin stepped into the spot previously occupied by David Baas, who left in free agency.It was a great pickup for the 49ers. Goodwin has been an anchor in the middle of...