The Denver Broncos' home-field advantage for Sunday night's opener against the Pittsburgh Steelers is already paying dividends, albeit an unfortunate one, as Steelers safety Ryan Clark won't play, according to an ESPN report.

Playing at high altitudes is problematic for Clark, as ESPN's Stephania Bell explains. Clark has a sickle-cell trait that affects red blood cells. Clark developed a season-ending illness while playing in a 2007 game in Denver. The illness cost Clark his spleen and his gallbladder, so it's not difficult to see why the Steelers wouldn't want to risk playing him in high altitude again.

Steelers coach Mike Tomlin sat Clark in what turned out to be a season-ending playoff loss in Denver in January. Clark is expected to travel and dress with the team, but will be reduced to a sideline supporter.

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