HOUSTON (AP) - It's become a running joke at Houston Texans' training camp: Who will be the next linebacker to go down with an injury?
With the start of the regular season less than three weeks away, coach Gary Kubiak isn't doing much laughing.
The Texans need to find a replacement for Brian Cushing, who's suspended for the first four games for testing positive for a banned substance. The two players pegged as front-runners to take his spot _ Xavier Adibi and Danny Clark _ have been hurt during training camp, and Kubiak has given no timetable for their returns.
Adibi (groin) and Clark (knee) ran conditioning drills on Wednesday.
Rookie Darryl Sharpton, another possibility to fill in for Cushing, sprained his knee in Saturday's 38-20 loss to New Orleans and was limited in Wednesday's practice.
Kevin Bentley, who's played mostly special teams in two seasons in Houston, played Cushing's position in practice on Wednesday. He turned his ankle in the New Orleans game.
"We all joke about it now, 'cause we're all in the training room together," said All-Pro middle linebacker DeMeco Ryans, who's stayed healthy during camp.
Kubiak said another option _ and one he'd rather avoid _ is moving 2009 starter Zac Diles from the weak-side position to Cushing's spot, and moving Bentley or Sharpton into Diles' role.
Kubiak doesn't anticipate the Texans signing a free agent to fix the problem, at least for now. Houston plays Dallas on Saturday, and Kubiak plans to play his starters for three quarters.
"We're at a point right now where it's tough to bring somebody off the street and throw them in a game," he said. "We've just got to work through the problem. It may be a thought when we go into next week, but the way we're approaching this game is basically with our starters. We've just got to push through and make it work."
Sharpton seems to be up to the task. The 5-foot-11 Sharpton was Houston's fourth-round draft pick out of Miami, and he's impressed both teammates and coaches.
"He's in the mix right now," Kubiak said. "He's made statements since he's been out here in camp."
Sharpton started 30 games at Miami _ 18 at middle linebacker, nine at strong side and three at weak side. With Ryans' mentoring, Sharpton has tried to learn how to play all three spots at the pro level.
"You never know what's going to happen, where they might need to plug you in," Sharpton said. "When they do, when your number is called, there can't be any drop-off."
Despite the alarming number of injuries, Ryans thinks the Texans have more depth in the linebacking group than they've had in his four seasons. Diles started 14 games last season and Bentley started the last seven games in 2008 after Diles broke his leg.
Ryans is confident that Adibi and Clark will return in time for the regular season opener. And after four games, Houston will welcome back Cushing, the 2009 Defensive Rookie of the Year.
"We've got our hands tied at the linebacking position, because we have so many guys that are down," Ryans said. "But it's good that we have the experience we have. With guys going down, it doesn't bother me as much as it would have in the past.
"It's part of football," he said. "The linebacker position is very tough and very demanding. We have tough guys, and they'll step in and they'll be ready to go when the time comes."
Kubiak also said tight end Owen Daniels has been medically cleared to return to practice. Daniels has been out since tearing a right knee ligament in the eighth game of last season. Kubiak said Daniels should be ready for the Texans' regular-season opener against Indianapolis on Sept. 12.