Terms of the deal, from ProFootballTalk, are $37.2 million over the five years, with Davis set to pocket $17 million in guaranteed cash. Prior to the extension, Davis was under contract in San Francisco through the 2014 season, and PFT also reports that this new extension will add on to that, making him a 49er now through 2019.
David Fucillo at Niners Nation says that Davis' improvements in 2012 led to this lengthy extension:
The timing is pretty good on this considering Jason Hurley opened his discussion of pending 2014 free agents with a look at Davis and Mike Iupati. Davis struggled with consistency his first two years, but took a huge step forward in year three, and was one of several reasons the 49ers had the best offensive line in football this past season.
San Francisco traded up to the eleventh overall pick in the 2010 NFL Draft to select Davis out of Rutgers University. Since then, the 49ers' offensive line has ascended to one of the league's best, a major reason for the team's average of 155.7 rushing yards per game last season, which ranked fourth-best in the league. Davis, 23, has started in every game of his three-year career.