Coach Gary Kubiak said earlier Monday that Schaub was injured on a quarterback sneak coming out of the end zone late in the second quarter of Houston's 37-9 win over Tampa Bay on Sunday. Schaub stayed in the game, but threw only three passes.
Kubiak said the team was bringing in a specialist from Indianapolis to evaluate Schaub, and the quarterback would fly to Charlotte, N.C., later this week to undergo further examination.
Joby Branion, Schaub's agent, did not immediately return a phone message or e-mail from The Associated Press.
The Texans (7-3) have won four in a row and share the AFC's best record with Pittsburgh heading into their bye week. Kubiak said sixth-year veteran Matt Leinart will start at Jacksonville on Nov. 27.
"It's just something we'll have to deal with," star receiver Andre Johnson said Monday night. "Hopefully, Matt won't miss the whole season. We're not sure exactly what it is, but we do know he'll have to miss some time. We're just going to rally around Matt Leinart, and I think he'll go out and do a great job."
Johnson has missed six games with a right hamstring injury, but expects to return for the Jacksonville game. He was on the sideline Sunday and said Schaub was "limping a little bit," but said he was OK.
"To come in and here that today," Johnson said, "it was kind of like, 'Wow.' Now you're hearing rumors that it's possible he could miss the rest of the season and things like that. So it's kind of like, where did all of that come from?"
Leinart, the 2004 Heisman Trophy winner for Southern California, re-signed with the Texans in the offseason after not taking a snap in 2010. He turned down other offers to return to Houston because he was comfortable with Kubiak and his offensive system.
Houston rank eighth in total offense this season (396.2 yards per game).
"Your time's going to come, and you've got to be accountable for when that opportunity comes," Leinart said. "They know that I work hard and I study hard and I'm prepared very well. We'll going to take this and go game-by-game and I don't think much is going to change."
Leinart guided Southern Cal to national championship games after the 2004 and `05 seasons, and went 37-2 as a starter in college.
He was drafted 10th overall by Arizona in 2006 and appeared in 12 games as a rookie under coach Dennis Green, throwing 11 touchdowns and 12 interceptions. He broke his collarbone in the fifth game of the next season, Kurt Warner took over and Leinart was mostly a spectator over the next 2½ seasons.
Leinart talked openly during training camp about earning another starting job. Now he'll get it, just not under the circumstances he wanted.
"I'm bummed. My heart goes out for him," Leinart said. "But he knows and everyone knows that in this profession, things happen, and the next guy has to step up. That's my job and my responsibility.
"That's what I've wanted for a long time, and that's what I've worked hard for every day and prepared for every day," he said. "It's a great opportunity. I'm just excited about the chance."
Kubiak has been increasing Leinart's repetitions in practice, and he's confident Leinart is ready.
"He's played in big football games in this league, he's played in big football games in college," Kubiak said. "Matt's been around it. The key is the whole team rallying around him, and playing well as a team. Matt doesn't have to go win a game, the team has to go win a game. We'll rally around him and get him ready to go."
Schaub, acquired in a trade with Atlanta in March 2007, has started every game for Houston since the start of the 2009 season. Kubiak would not say if Schaub would miss the rest of this year.
"There's a lot of things reported," Kubiak said. "He's going to be in a boot throughout this week, and then the evaluation process will continue."
Schaub joins the growing list of Houston stars sidelined with injuries this season.
In addition to Johnson, sacks leader Mario Williams was lost for the season with a torn chest muscle in a loss to Oakland on Oct. 9, running back Arian Foster missed two of the first three games with a strained left hamstring, and starting safety Danieal Manning has missed three games after breaking his left fibula.
Somehow, the Texans have managed to stay on course for their first playoff berth. Houston hasn't trailed in a game in four weeks and won by an average of 22.5 points across that span.
Johnson says the Texans have experienced so much adversity in past seasons, they understand how to cope with it now.
"In the past, when we had injuries, it always hurt us," Johnson said. "Everything we've been through as a team, you learn from those things and all the obstacles we've been through.
"Losing our quarterback, I still feel very comfortable, I still feel very positive about it. We'll pick up the slack, man. Everyone will step their game up and we'll keep going in the right direction."
The Texans have the NFL's No. 1 defense (269.7 yards per game) and the third-best rushing offense (158.1 yards per game), with Foster and Tate both ranking among the top 10.
"We're going to get tested even more now, so we'll have to call on everybody to do that," Kubiak said. "We do have a lot of confidence right now in what we're doing and we just got to keep our chin up and move forward."
Information from The Associated Press contributed to this report.