San Francisco 49ers nose tackle Mike Purcell (64) returns an interception by Dallas Cowboys quarterback Dustin Vaughan, bottom, for a touchdown during the first half of an NFL preseason football game in Santa Clara, Calif., Sunday, Aug. 23, 2015.
San Francisco 49ers nose tackle Mike Purcell (64) returns an interception by Dallas Cowboys quarterback Dustin Vaughan, bottom, for a touchdown during the first half of an NFL preseason football game in Santa Clara, Calif., Sunday, Aug. 23, 2015. Tony Avelar AP
San Francisco 49ers nose tackle Mike Purcell (64) returns an interception by Dallas Cowboys quarterback Dustin Vaughan, bottom, for a touchdown during the first half of an NFL preseason football game in Santa Clara, Calif., Sunday, Aug. 23, 2015. Tony Avelar AP