While Manning insisted he's feeling fine after needing 12 stitches Monday night to close a cut on the left side of his head, Coughlin said the team is concerned that wearing a helmet might break the stitches or irritate the wound.
Jim Sorgi also didn't practice because of shoulder and rib injuries, and Coughlin wasn't sure whether the backup quarterback would play in the Giants' first home game at the New Meadowlands Stadium.
Rhett Bomar took all the snaps Wednesday, though the Giants signed QB Dominic Randolph to provide some depth, according to the New York Star-Ledger.
"I am not going to rush things," said Coughlin, who said he has never conducted a training-camp practice with one quarterback. "If the doctors say it's OK for him (Manning) to throw, then maybe he'll do some throwing. But, he definitely is not going to put the helmet on."
Manning was scheduled to be examined after practice by team surgeon Russell Warren, but the results wouldn't affect the decision to sit to the 29-year-old, who wore a baseball cap at practice. Coughlin didn't know when Manning would be back.
Sorgi's status is a wait-and-see proposition, mostly because of a sore shoulder that resulted from a hit he took on a fourth-quarter touchdown pass against the New York Jets on Monday night.
"He is sore and could not have thrown today," Coughlin said.
Earlier in the day, Manning sounded like someone who knew he wasn't going to play.
"I physically feel fine," Manning said after lunch. "I threw some balls today. I ran around, I know what is going on. I'm all there. It's just a matter of getting the helmet on."
The Giants could put extra padding in the helmet, but it seems an unnecessary risk for a preseason game.
"When it is preseason, you have time to get things healed up," Manning said. "It's time to be smart."
Manning refused to show reporters his cut, but he took his cap off on the field and revealed a sterile pad covering the stitches.
Manning lay on the field for a few seconds, then summoned the team's athletic trainers after seeing blood gushing into his hand. He said he wasn't in pain at that point and knew he didn't have a concussion. He was concerned because he couldn't see the extent of the cut.
"You get a little worried," he said.
Manning said his wife, Abby, was at the game and came down to the locker room while he was being treated.
"She's more concerned about the scar I'll have than anything else," Manning quipped.
Manning said he took an ImPACT test, a computerized evaluation of memory, brain processing and visual motor skills, on Wednesday. Coughlin said the results were normal.
Teammates were glad to see Manning walking around, and offensive linemen Shaun O'Hara, David Diehl and Rich Seubert arrived at lunch wearing huge bandages over the left sides of their heads.
"I wouldn't expect anything less," Manning said, shaking his head.
He later got back at O'Hara, saying that while he didn't pass out after being cut, the center did when he looked at it.
"I saw the look in his eyes and said this must be pretty bad, it's not a little scratch," Manning said.
"I'm a little sore," Sorgi said Wednesday. "I took a couple of good shots. We'll see how it goes, ice down and get some treatment and be ready to go."
Sorgi laughed about comparing his injury to Manning.
"He got 12 stitches. I didn't get stitches," Sorgi said. "I'll say I caught the good end of that."
Copyright 2010 by The Associated Press