He played a key role in the season opener upset against the University of Notre Dame, when he teamed with linebacker Chris Garlich to stop running back Vagas Ferguson on fourth-down at the Tigers one-yard line.
Petersen was selected by the Dallas Cowboys in the fourth round (105th overall) of the 1980 NFL draft, with the intention of playing him on the offensive line.
In 1981 he was named the starting right guard, after Robert Shaw went down with a career ending knee injury in the second game, that required previous starter Tom Rafferty to play center.
In 1982, he started all games during a strike shortened season, receiving second-team All-Pro honors.
On August 19, 1986, he was placed on the injured reserve list after suffering a serious left knee injury that would eventually forced him into early retirement.