Still, the Arizona star wide receiver said he expects to play. So does quarterback Carson Palmer, who is dealing with a high ankle sprain.
Both were injured Sunday in the Cardinals' 37-34 overtime win at Tennessee.
The Cardinals are a battered bunch as they prepare for the Seahawks, a game where Arizona is a big underdog and needs an upset victory to greatly improve its playoff chances.
Safety Rashad Johnson was in a walking boot at practice Thursday because of a high ankle sprain, and tight end Rob Housler missed the Tennessee game with a groin injury.
"This week everybody is trying to get back," Housler said. "We know how important it is."
Although he said he practiced in full, Fitzgerald was listed as limited on the Thursday injury report. So were Palmer, Housler, linebacker Karlos Dansby (foot), running back Rashard Mendenhall (finger), linebacker Matt Shaughnessy (groin) and linebacker Dontay Moch (hamstring). Johnson did not practice.
Fitzgerald's concussion occurred when he was trying to field an onside kick at Tennessee and took a severe hit from Jackie Battle. Fitzgerald said he doesn't remember the hit, only getting up and walking off the field. He watched it on video on Thursday.
He said he thought it was a clean hit. Fitzgerald said that, as a wide receiver, he can brace himself for anticipated hits. But on the "hands" team for an onside kick, "I have no idea where the guy's coming from."
"I'm in a vulnerable position. He just caught me," Fitzgerald said. "You know Muhammad Ali got knocked out a couple of times. It just happened. He caught me flush."
Fitzgerald said his final test will come in a meeting with a neurologist on Friday. He said the doctor has no affiliation with the team.
"He's not even a Cardinals fan," Fitzgerald said.
Fitzgerald said he's well aware of the issues surrounding concussions in the NFL and insisted this is his first one.
"I have an opportunity to do something I truly love doing playing ball," he said. "That's kind of how I think about it. I obviously understand all of the ramifications and have seen the studies and seen those guys that have dealt with issues in the past."
Fitzgerald said he tested himself on Wednesday with exercise under the direction of team physical therapist Chad Cook "just to get my heart rate up and make me exhaust myself a little bit to see how I felt."
"And I was feeling fine," he said, "had no dizziness or headaches or anything like that, so they said it was cool for me to ramp it up a little bit and go out there and practice."
Fitzgerald has played in 104 consecutive games, counting the playoffs.
"I've never missed a division game in my life," he said, "and I don't plan to start (missing them) this weekend."
The concussion forced Fitzgerald to the sideline for the overtime period against the Titans. Palmer injured his ankle early in the game but got it taped up and stayed in.
"Ankle's good," Palmer said on Wednesday. "Got a lot of treatment on it and (I will) be ready to roll."
Johnson had just stepped in to the starting free safety position following the season-ending knee injury to rookie Tyrann Mathieu. If Johnson can't go, the job will fall to rookie Tony Jefferson, an undrafted free agent from Oklahoma. Jefferson put the pressure on Tennessee quarterback Ryan Fitzpatrick that led to Antoine Cason's crucial interception in overtime.
With Mathieu out, Cason will get more time at the nickel cornerback.
With Mathieu and Johnson ahead of him, Jefferson said he didn't know if he would get the chance to play.
"I just knew I had to be ready when it was a time," Jefferson said. "It's time now."