This year’s “Hard Knocks” series with the Dallas Cowboys will mark the first time one of its teams is in the Hall of Fame game. It is fitting because the creator of the series was enshrined into the hall earlier this year. “Hard Knocks,” which started 20 years ago, is one of Steve Sabol’s many legacies at NFL Films that continue to live on. Sabol, who was 69 when he died from brain cancer in 2012, is one of three contributors part of the hall’s 2020 Centennial Class, which honors 20 former players, coaches, and contributors across all eras of the NFL’s first 100 years. “I would like to think it’s no coincidence that this is the year that ‘Hard Knocks’ will be at the Hall of Fame. I think Steve is still watching over us,” said NFL Films’ Ken Rodgers, the senior coordinating producer of “Hard Knocks.” Sabol joins …