The 49ers offensive line had been remarkably stable over two seasons. Through the game at New Orleans Nov. 17, the same starting five had made 26 consecutive starts together.Left tackle Joe Staley, left guard Mike Iupati, center Jonathan Goodwin, right guard Alex Boone and right tackle Anthony Davis not only were good, but durable – a huge component in the success the 49ers have enjoyed.But now, as the 49ers prepare to host the Seattle Seahawks Sunday and wrap up the final four games of the 2013 regular season, the team's offensive line has been forced to adapt, improvise and overcome a pair of injuries.First, Iupati was lost in the Saints game. Now, the 49ers will likely be without Staley this weekend – and probably longer – after suffering an injury early in the victory over the Rams.Eric Branch of the San Francisco Chronicle, citing a source close to the situation, reported that Staley sustained a sprained medial collateral ligament (MCL) and was scheduled for an MRI exam Monday to determine the severity of the injury. It's the same type of injury sustained by Iupati vs. the Saints, and Iupati has not played since.As he left the field at Candlestick Park...