[1] Frederick was selected by the Dallas Cowboys in the fifth round (137th overall) of the 1977 NFL draft, to convert him into an offensive lineman.
As a rookie, he played on special teams and backed up Ralph Neely at left tackle, who was bothered by an injured knee.
In 1978, he was named the starter at right tackle to replace Pat Donovan who moved to the left side to take the place of the retired Neely.
In 1979, he was one of the last cuts in preseason, but was brought back after rookie tackle Richard Grimmett suffered a knee injury one week before the season opener.
During the Bears' Super Bowl run in 1985,[5] he was mostly used as an extra tight end in goal line situations.