Johnson, who is fourth in the NFL in receiving yards (1,216), revealed Friday that the high ankle sprain he has battled virtually all season has worsened. An MRI on Monday showed further damage to his ankle.
"I had the high ankle sprain and I was working on the front part of my ankle, and I got caught when I was down on the ground and got tackled in the Baltimore game (Dec. 13)," Johnson said. "My joint kind of got jammed up a little bit, and it's affecting me in the back now, kind of like around the Achilles' area. When I run now, I kind of feel more pain than I was feeling before. In the MRI, it just showed that.
"We didn't think that it could get any worse, and it's gotten worse. Like I said, I'm just trying to do everything I can to make sure I can play on Sunday."
Johnson didn't practice all week, although he did jog Friday. He's listed as questionable on the team's injury report.
"You just have to see what happens," Johnson said. "I've been getting a shot the past few games, and I can still feel pain in there. The part that's (different), it's only so much of it you can numb up, and they can't numb up the joint. And that's what's really starting to bother me pretty bad now."
Johnson also is concerned about the potential for long-term damage to the joint.
"It's something you have to think about," he said. "You don't want to do anything to set yourself back or even set your team back. You don't want to have anything crazy happen and then you have to have surgery and stuff like that."
Running back Arian Foster (hip) and quarterback Matt Schaub (right elbow) headline a large list of Texans who are probable. The group includes linebacker Brian Cushing (knee, ankle, foot), kicker Neil Rackers (hamstring), defensive linemen Damione Lewis (illness) and Mark Anderson (knee), and offensive tackle Duane Brown (shoulder). Rackers and Lewis didn't practice Friday, and Cushing was limited.