Pittsburgh Steelers safety Ryan Clark, one of the team's leading defenders, won't play in Sunday's NFL playoff game in Denver because physical exertion in the city's mile-high altitude may aggravate Clark's sickle cell trait.
"Looking at data and all the variables he is at more risk, so we're not going to play him. It's just that simple," Steelers coach Mike Tomlin said Tuesday, according to CNN affiliate WPXI-TV.
"If he is in any more danger than any of the other 21 men on the field, then we err on the side of caution," Tomlin said at a news conference.
"It is a big game for us, but it is a game," he said.
After a 2007 game in Denver, Clark had his spleen and gall bladder removed and lost 30 pounds from sickle cell complications.
But Clark told ESPN he thought he could play in Denver this weekend despite the risks.
"I talked to my doctors and we actually had a plan in place for me to play. All things pointed to me going until (Tomlin) told me I can't. He said he wouldn't have let his son play and so I'm not playing either," Clark told ESPN.
After hearing that, Clark said he couldn't argue with Tomlin's decision.
"I appreciate coach caring about me more than this football game," he said in the ESPN interview.
The sickle cell trait is an inherited condition that occurs when one parent passes to a sickle cell gene to a child, according to the Centers for Disease Control and Prevention. Those with the trait do not usually exhibit symptoms of sickle cell disease, which occurs when the child inherits the sickle cell gene from both parents.
Sickle cell disease is a blood disorder in which normally round red blood cells, which carry oxygen throughout the body, become crescent- or sickle-shaped. They also become hard and sticky and tend to die early, according to the CDC. And because of their shape, they can become stuck in blood vessels leading to problems including infection and stroke.
But the CDC cautions that those with sickle cell trait can experience complications during both athletic activity and when at high altitudes. Denver, known as the Mile-High City, is 5,280 feet above sea level. Pittsburgh is about 770 feet above sea level.
Clark has been the Steelers' busiest defender this season, according to ESPN.com. He has been on the field for 1,009 snaps this season, or 98.7% of the team's defensive plays. He led the team with 100 tackles.
Clark will be replaced by Ryan Mundy in the starting lineup.