FRISCO -- The Denver Broncos struggled to defend the run last year, allowing 130.3 yards per game to rank in the bottom five across the league.How about against the Chargers on Monday night, in their 2017 opener? The Broncos allowed less than half that, holding Melvin Gordon and the Los Angeles Chargers to just 64 yards in a 24-21 Broncos win.What changed?"When you try to stop the run game, it's really about gap integrity," Broncos coach Vance Joseph said Wednesday.