What are 49ers' options in Boone holdout?

Daily 49ers blog for NBC Bay Area website: Alex Boone's holdout is understandable, given his performance on what was a contract for a backup player. But if his time away is extensive, who takes his place at right guard? http://www.nbcbayarea.com/news/sports/Niners-Have-Options-if-Boone-Holdout-Continues-267507601.html