Clark became almost deathly ill after playing in Denver's mile-high altitude two years ago, losing his spleen and gall bladder plus 30 pounds due to medical complications that ended his season. The Steelers (5-2) play in Denver again on Monday, and Clark and coach Mike Tomlin haven't decided if he will suit up.
"His physical health, his well-being, of course, is paramount," Tomlin said Monday. "We're going to attempt to do what's right, we're going to weigh all our options and we're going to come to a decision at some point later this week."
Clark practiced Monday as the Steelers returned from a full week off, and he has received medical clearance to play.
"I think before we considered anything, we needed to hear, 'OK, Ryan, you're at no extra medical risk to participate in this game than anyone else is,' " Tomlin said. "He and I have received that, but we're still going to proceed with extreme caution. We're not going to hurry this process."
The illness was blamed on Clark having sickle cell trait, but Clark has an additional condition that aggravated the problem, according to his coach. Numerous players with sickle cell trait have played in Denver without problems, Tomlin said.
Steelers wide receiver Santonio Holmes found out after the Steelers' 31-28 loss in Denver in 2007 that he also has sickle cell trait, a condition in which a person inherits one of the genes of sickle cell anemia, a blood disorder. Holmes plans to play in Denver.
"Ryan is a unique case where it's the sickle cell trait in combination with some other pre-existing medical issue that creates it," Tomlin said. "Santonio is not at any unique risk, unless he, too, shares that same medical situation, which I believe at this point he does not."
Steelers safety Troy Polamalu saw Clark when he was sick, and he understands how difficult his teammate's decision is. Monday's game could prove important in determining AFC playoff seeding unless the Broncos (6-1) or Steelers go into a steep slide.
"He almost lost his life the last time we played there, so it's kind of unfair to say I would or wouldn't [play] because I didn't undergo the torture and the suffering he had to go through," Polamalu said.
Steelers wide receiver Hines Ward and several other teammates all but said they hope Clark doesn't play.
"Whatever he decides, we're going to back him. But if it was me, personally, life is more precious than football," Ward said. "Any time you miss a game and don't feel injured, you want to play because that's one game you'll never get back. But you've got to look at the big picture. There's still a lot of football left and we'd rather have Ryan for the long haul rather than the short term."
To help prepare for playing in Denver, Ward said he expects Steelers players, including linebacker James Harrison, Polamalu and Holmes, to spend time in a hyperbaric chamber, which is used to treat altitude sickness.
The devices are expensive -- a portable chamber costs $16,000 to $20,000-plus, and a full-sized hospital unit can cost $1 million -- but Ward refers to his as "the fountain of youth." Ward said a hyperbaric chamber promotes the production of red blood cells, thus increasing energy and accelerating the recovery time from injuries.
"A hyperbaric chamber is a lot like training in Denver," Ward said. "I'll be in there every day this week. ... They're expensive, but they're well worth the investment."
Steelers running back Willie Parker missed practice Monday due to illness, but is expected to be ready for the Monday night game.