"It is tough," Ryans said. "It was heartbreaking to hear the news that you're done for the season."
Ryans jumped and fell to the turf on a touchdown by the Chiefs. He remained on the turf for a few minutes while trainers attended to him before being helped to the cart.
"I was planting to go make a play on the ball," he said of the injury. "I was trying to jump up and I couldn't push off my foot."
Ryans, a second-round pick in 2006, has had more than 110 tackles in each of his first four NFL seasons.
It's a major blow to a defense that was already struggling before the injury to its leader. The Texans got strongside linebacker Brian Cushing back last week after he served a four-game suspension for violating the NFL's policy on performance-enhancing drugs and will now have to adjust to the loss of Ryans.
"On our side of the ball, he is our Matt Schaub," defensive coordinator Frank Bush said. "He's the guy that leads our defense. He does everything for us. With him going down, it's going to be tough. We can't replace him. We've just got to try to move on with the guys that we have."
Weakside linebacker Zac Diles moved to the middle after Ryans went down Sunday. Bush would prefer to keep Diles at weakside and hopes Kevin Bentley will be healthy enough after the bye to take over for Ryans. He has been out with a knee injury.
"Anytime something like that happens, it's a blow to the team," Cushing said. "It's a blow to morale, but we have to play for him now."
Kubiak said the offense will simply have to carry the defense until it works out its problems. Star receiver Andre Johnson is ready to help do that.
"You really can't replace DeMeco," Johnson said. "His nickname is Captain ... so that goes to show you what he means to this football team. For us to lose him, it makes you feel like you can't catch a break. We just have to have some guys step up."
Ryans, the 2006 Defensive Rookie of the Year, finishes his season with 54 tackles.
Copyright 2010 by The Associated Press