Gerela graduated from Kalani High School in Honolulu, and played college football for the New Mexico State Aggies.
He was selected in the fourth round of the 1969 NFL/AFL draft by the Houston Oilers and played for them in the American Football League in 1969, as well as their first NFL season of 1970.
Gerela was a member of the Steelers' Super Bowl championship teams in 1974, 1975, and 1978, but was released before the 1979 season in favor of rookie Matt Bahr.
Gerela ranks fourth on the Steelers' all-time scoring list, behind Gary Anderson, Jeff Reed, and Chris Boswell.
In 1993, his son Ted Gerela was selected in the seventh round of the 1993 CFL Draft by the BC Lions as a linebacker from Rocky Mountain College.