Tyrone Area High School football coach John Franco’s Golden Eagles are the favorite to win the District 6 Class AA championship this year. They return nearly half their starters. They are state ranked. They’ve won their last 32 straight regular-season game and the last five meetings with archrival Bellwood-Antis — the last two by shutout. Improbable as it might seem, though, Franco is trying to pass Tyrone off as the underdog in this year’s renewal of the ‘‘Backyard Brawl.’’ ‘‘That’s the only way you can look at it,’’ said Franco, whose team will host this year’s clash with the Blue Devils on Friday at Gray-Veterans Memorial Field Friday night. ‘‘That’s how the kids look at it.’’ The basis for Franco’s rationale? A 42-0 pasting the Devils dropped on the Eagles in junior high when this year’s seniors were freshmen. If he needed any more reinforcement, he got it when Bellwood beat Tyrone in the junior varsity opener. ‘‘I think [our players] know how good they are.