Schaub took half the snaps in practice, his first significant work since he sprained his left ankle during a Aug. 31 preseason game against the Minnesota Vikings. He is listed as day-to-day.
Grossman, who led the Chicago Bears to the Super Bowl in the 2006 season, overtook Dan Orlovsky in the competition to back up Schaub after throwing two touchdown passes in the Texans' preseason finale. Orlovsky, a seven-game starter for the Detroit Lions last season, was scheduled to be the backup before Grossman's recent performance, which came after he missed two weeks of action because of an injury.
"Matt is hobbled, so they've got to be ready to go," Kubiak said. "But as I told Dan and Rex, I'm leaning toward Rex's experience and the way he handled himself, handled the team the other night. I'm kind of drawing from what I've seen him do in the past and (am) just very comfortable with him right now."
Grossman was excited about the decision, but he said it won't change anything he does.
"I've got to prove myself every practice and every time I go out there," he said. "You get graded and you get judged basically every time you throw the football. So I'm still going to have that same sense of urgency."
The status of wide receiver Kevin Walter and safety Eugene Wilson also are uncertain because of injuries.
Walter, who was second on the team with 899 receiving yards and eight touchdowns last season, has a hamstring injury. Wilson was injured on an illegal crackback block delivered by Vikings quarterback Brett Favre, whom the NFL fined $10,000.
Cushing missed all four preseason games because of a sprained knee, but he is healthy and expected to start at strongside linebacker.
Middle linebacker DeMeco Ryans is confident that Cushing is up to the task, but he has been trying to help the first-round draft pick in the days leading up to his NFL debut.
"I stay on him, always asking him questions to make sure he's into what we're doing, into our game plan and making sure we're both on the same page," Ryans said. "The more me, him and Zac (Diles) communicate, the easier it's going to be for all three of us."
Robinson missed all of camp in a contract holdout before reporting Sunday. He is expected to start.
"The thing that concerns me is they have not all been working together, but it's time to go to work together," Kubiak said. "I think they all understand it, too. So the sense of urgency, the attention to detail in getting ready to play, has got to be good anyway, but it better be great this week."
Robinson practiced with the team for the first time Tuesday and was encouraged afterward.
"I thought I'd feel a little rusty, but I felt fine, like I had been out there for a while," he said. "I would say it was a good start ... it felt good to be back out there with the fellas and running around a little bit."
Copyright 2009 by The Associated Press