Steelers QB Ben Roethlisberger believes he suffered his sprained shoulder and rib injury when he hit the ground after being tackled by a pair of Chiefs defensive linemen, including Justin Houston (shown pursuing Roethlisberger earlier in Sunday night's fateful game). (US Presswire)

It was reported soon after Steelers QB Ben Roethlisberger was knocked out of the game Monday night that his injury was “unusual.”

Try first-time-in-14-years unusual.

Rugby unusual.

Roethlisberger said his doctor told him that it’s difficult to provide an educated prognosis for a possible return to game action because there is no case study or precedent for an NFL player -- let alone a quarterback -- to have sustained exactly what ails him.

In fact, it’s difficult to find a case study or precedent for any athlete to have sustained what Roethlisberger has.

“From what he told me, it was a 1998 rugby player or something,” Roethlisberger said. “We’ll just try to keep talking to people to get an expectation because we just don’t know (a prognosis).”

Roethlisberger said he has a sprained SC joint in his right (throwing) shoulder, but the bigger concern is the dislocation of his first rib. The rib has the potential to puncture his aorta, obviously a potentially dangerous situation.

Roethlisberger has been ruled out for Sunday night’s AFC North showdown with the Baltimore Ravens, leaving veteran QB Byron Leftwich to start in his place.

When asked if his injury was potentially season-ending, Roethlisberger said, “I don’t think so. I don’t know, though. I’m not a medical expert.”

Big Ben termed his pain level at a nine on a scale from 1-10 and said he is forced to sleep while sitting upright (he’s only had four hours of sleep the past two nights, he said). Roethlisberger said his range of motion isn’t limited so much as that when he does move, it’s painful. His rib has popped out of place when he attempts movement.

Roethlisberger believes the injury occurred more when he struck the ground than when he was hit by Chiefs defensive linemen Justin Houston and Tamba Hali.

“When I hit the ground is when I heard the crunch and the crack and stuff,” Roethlisberger said. “So that’s when I knew for sure.”

One thing Big Ben and the rest of the Steelers don’t know for sure is when he will be able to play again.

“I’m going to get back as soon as I can,” Roethlisberger said. “I’m just getting treatment and trying to do what I can.”

Follow Steelers reporter Chris Adamski on Twitter @CBSSteelers and @BuzzsawPGH.