The San Francisco 49ers fear they will lose star wide receiver Michael Crabtree to a torn Achilles tendon suffered in off-season workouts Tuesday.

The San Francisco 49ers signed defensive tackle Tank Carradine and tight end Vance McDonald to four-year contracts on Thursday.

Michael Crabtree's unfortunate injury changes things in San Francisco and on Draft Day. Our Jamey Eisenberg re-examines the 49ers offense heading into 2013.

SAN FRANCISCO, May 22 (UPI) -- San Francisco 49ers wide receiver Michael Crabtree has undergone surgery for a torn Achilles tendon, Coach Jim Harbaugh said Wednesday.

San Francisco 49ers wide receiver Michael Crabtree has had surgery to repair a torn Achilles tendon but is not expected to miss the entire 2013-14 season, the National Football League (NFL) team said on Wednesday.