Smith was characterized as a game-time decision by coach John Harbaugh.
Smith was favoring his sprained right knee, wearing a brace and looking gimpy and uncomfortable running pass patterns at half-speed. If Smith plays Sunday against the 2-11 Jacksonville Jaguars, it would be a surprise even though he's officially listed as probable.
Smith has never missed a game in the NFL.
"It's definitely tough, especially because I haven't missed a game since I broke my leg in the summer going into my junior year of high school," Smith said. "I'm not used to it. I'm not used to missing practice. I don't really like it too much, but I got to get healthy and I got to make the right decision. We'll see what happens on Sunday."
Smith played 15 snaps against the Miami Dolphins last week after his knee swelled up during warmups before kickoff. He wasn't targeted with a single pass.
"He looked pretty good," Harbaugh said. "We'll see how he is Sunday."
Smith said he plans to test out his knee during warmups.
"You got to test it out and see because it might feel amazing," Smith said. "It may feel perfect. Another day or two will definitely help."
Harbaugh said Monday that tests revealed no ligament damage for Smith and he was diagnosed with a sprained knee.
"I think sometimes coach is better, for coach to save me from myself," Smith said. "I've never had to make a call like that. I can play through pain, but it's a matter of weighing is it worth lingering for a few weeks. Is it going to be ready on Sunday? I don't know the answer yet. It will be resolved here soon, hopefully tomorrow. I'd love to be out there Sunday, but we'll see what happens."
Veteran wide receiver Steve Smith was at practice Friday, but wasn't dressed out. Harbaugh said Smith has a cold, but should be fine for Sunday. He was listed as a probable.
Veteran outside linebacker Terrell Suggs was given a day off.
Rookie tight end Crockett Gillmore returned to practice from a back injury, but he wasn't doing much and didn't have his normal mobility. Gillmore is listed as questionable and not expected to play.
Rookie running back Lorenzo Taliaferro has a sprained foot and hasn't practiced all week. Taliaferro is in a walking boot and isn't expected to play Sunday, according to a source.
Taliaferro is listed as questionable.
Reserve offensive guard Jah Reid is questionable after aggravating his right hand, which he broke and had surgery.
Cornerback Anthony Levine has been cleared under the NFL concussion testing protocol and is set to play Sunday. He's listed as probable.