Pierce didn't practice Monday. Before he can return, he has to take and pass a mandatory baseline neurological test under NFL medical guidelines governing concussions.
Harbaugh said that Ravens trainer Mark Smith informed him that Pierce is "feeling a lot better."
"Nowadays, with those things, I don't take any stock in that until they tell me that he's back," Harbaugh said. "The concussion thing is just hard to predict."
Tight end Owen Daniels returned to practice on a limited basis, doing individual drills.
"He got back out there," Harbaugh said. "We don't want to bring him back too fast."
Daniels missed the past two preseason games and weeks of practice with leg soreness that Harbaugh has characterized as a non-injury.
Harbaugh said he expects Daniels, a two-time Pro Bowl selection, to be a part of the team this season.
"I don't anticipate it affecting his status," Harbaugh said. "There's no tear, there's no pull. There is swelling in the legs."
Reserve nose tackle Terrence Cody remains on the physically unable to perform list after undergoing offseason hip surgery. Although Cody has made progress, Harbaugh was noncommital on Cody's status for the regular season.
The Ravens could shift Cody to the reserve PUP list, which would require him being out for at least the first six games of the regular season. The Ravens could also cut Cody or place him on injured reserve.
"I don't want to say," Harbaugh said. "We have a couple of options. He's progressing well. He's done a really good job. Whether he's ready to play or not is undetermined."
Strong safety Matt Elam didn't practice due to a relatively minor leg muscle issue from the game, according to Harbaugh.
Wide receiver Kamar Aiken didn't practice due to a migraine.