Injuries — freak and common — are part of professional sports, and especially professional football. The frustrating thing about that, of course, is that the majority of injuries are random. To be successful, you either have to have luck on your side or you have to be particularly deep and prepared to deal with the fractures and sprains and tears that come your way.

But what’s happening to Ryan Clark just feels wrong.

It’s official. Clark won’t play Sunday when the Steelers travel to Denver for their wild-card playoff game. It’s not because of an injury — Clark’s perfectly healthy — or a suspension, or anything else related to the game of football. It’s because he has a medical condition called sickle cell trait.

The condition essentially means that Clark can play in any of the league’s 31 stadiums, except Sports Authority Field at Mile High, where the altitude can quite literally destroy Clark’s organs. Regardless of how important the game is, there was never any way Clark could play. He had to have his spleen and gallbladder removed when he attempted to do so in 2007.

So Tim Tebow’s magical run will cost Clark a playoff game, and will force the Steelers to play shorthanded on defense on the road.

The Steelers didn’t need Clark to easily defeat the Broncos at Mile High back in 2008, with backup Tyrone Carter playing a big role in Clark’s stead. At that point, Carter was an experienced vet with 39 starts under his belt.

Clark’s replacement Sunday — 2008 sixth-round pick Ryan Mundy — will only be making his third career start. Playing in place of Troy Polamalu last December, he had 12 tackles in two games against the Jets and Panthers.

The good news is that the Steelers might be able to afford being less than 100 percent in the secondary against Tebow and the Denver offense, which doesn’t pose much of a threat through the air. Clark did lead the team in tackles this season, and they might miss his ability to turn into a human hit-stick, but his absence is unlikely to be a game-changer against a team that averaged only 158 passing yards per game and was ranked 31st through the air during the regular season.

No, to beat the Broncos, you have to be healthy up front and in the linebacking corps. That’s why this was a good news/bad news day for Pittsburgh, who learned it will probably have LaMarr Woodley back from injury on Sunday.