Broncos Offense? Or Broncos' Offense?

We observe the city name replacing the mascot rule, too. Meaning, it should be the Broncos offense. At least, that's the way it was explained to me by someone who's opinion I deeply value.

 

But it would be ...
The Broncos' two-minute offense.

 

Denver's offense has struggled mightily while the Broncos' defense has tried to carry the team.

So, yes, you use the apostrophe. At least, you should. If somebody tells you different, send him back to second-grade English class for remedial education at once.

And it shouldn't be constructed that way -- the phrase "the Denver defense" contains an extraneous the that should easily be removed, forcing the use of the possessive Denver's.

Evidently that person failed second-grade English.