ESPN NFL

Fourth-year veteran right guard Anthony Herrera, a key to the Minnesota Vikings' dominant running game and to the success of rookie tailback Adrian Peterson, has signed a five-year contract extension that will keep him off the free-agent market next spring.

The extension, first reported by the Minneapolis Star-Tribune and subsequently confirmed through league salary update documents, has a base value of $13.75 million and a maximum worth of about $15 million. It includes $5 million in guarantees.

Herrera, 27, is playing the 2007 season under the one-year restricted free-agent qualifying offer of $850,000 that he signed in the spring.

Without the extension, Herrera would have been eligible for unrestricted free agency after the 2007 season.

A former University of Tennessee standout and native of Trinidad, Herrera replaced seven-year veteran Artis Hicks at right guard after the first four games of this season, and his move into the lineup coincided with the emergence of the Minnesota ground game. The Vikings were a solid running team in the first four games, averaging 135.0 yards on the ground, but have averaged 207.5 yards with Herrera in the lineup.

Minnesota statistically leads the NFL in rushing, at 177.9 yards per game. Despite starting only six games and missing last week's contest because of a knee injury that is expected to sideline him this week as well, Peterson is the league's leading rusher, with 1,081 yards.

Herrera originally entered the NFL as an undrafted college free agent in 2004 and played the first three seasons of his career for minimum base salaries.

He started six games at left guard in 2005, his second season in the league, but then made just two appearances in 2006, coach Brad Childress' first season with the franchise. In four years, Herrera has appeared in 22 games and started 12 of them.

Len Pasquarelli is a senior NFL writer for ESPN.com.