Johnson, who was injured in a Week 4 game against Pittsburgh, said Tuesday he has "no doubt" that he will be on the field for Houston's next game, which is November 27 at Jacksonville.
"I plan on playing," he said.
Head coach Gary Kubiak said he won't know until sometime next week if Schaub will be able to come back at all this season, putting pressure on Leinart to keep the AFC South-leading Texans on track to make the playoffs.
The former USC star hasn't started a game since 2009 with the Arizona Cardinals.
"He's been working extremely hard with our team. Obviously his role changes right now, but he's excited and I'm excited for him," Kubiak said. "It's a great opportunity for him. I know it also helps that Andre's fixing to come back with him."
Johnson, who had surgery two days after he was injured, had 25 catches for 352 yards and two touchdowns in the first four games this season and has scored 52 touchdowns with 9,516 receiving yards since 2003.
The Texans have won four games in a row, improving to 4-2 since Johnson went down.