In addition to signing a pair of mid-round tackles from the 2010 NFL Draft, the Oakland Raiders placed offensive tackle Elliot Vallejo on the "Reserve/Retired" list on Friday.

Vallejo, who played his college ball at UCLA before transferring to UC-Davis, began his NFL career with the Arizona Cardinals, who signed him as an undrafted free agent in 2007. The 6-7, 315-pound tackle spent the first two years of his career shuttling between the Cardinals' active roster and practice squad.

Vallejo fractured his kneecap during last year's training camp, and the Cardinals waived him with an injury settlement in September. Vallejo was a street free agent until spending a week on the Raiders' practice squad in December, and he was re-signed by the Raiders to a one-year deal on June 8.

No reason was given for his abrupt retirement from the National Football League.