SAN DIEGO (AP) - The San Diego Chargers signed former Arizona Cardinals guard Rich Ohrnberger to a one-year contract Thursday.

Heading into his fifth season, he has played in 18 career games and started four.

He was drafted by New England in the fourth round in 2009 out of Penn State. He played in five games his first two seasons with the Patriots, seeing limited time at right guard and on special teams. Ohrnberger spent the 2011 season on injured reserve due to a head injury and was released in February 2012. He signed with Arizona and played in 13 games last year, making two starts at both right guard and center. He suffered a knee injury on Dec. 9 against Seattle and was placed on injured reserve.

Ohrnberger becomes the sixth unrestricted free agent to join the Chargers, and the third offensive lineman.