CHARLOTTE, N.C. -- For the second time in three weeks, Panthers star quarterback Cam Newton takes a hit, stumble and fall that made us all say, "Oh, no."

"You kinda get this in the chest, like, 'oh my goodness, that was one of those shots, that was one of those shots to the head,'" says former NFL safety Eugene Robinson.

That shot to the head took Cam Newton out of the Panthers' game and into an independent doctor's office for the NFL's concussion protocol.

That's the right call, Robinson says.

"You ask any player and they'll tell you, 'yeah, I'm alright.' Everybody says I'm alright," Robinson says.

He ought to know: Robinson suffered at least three concussions during his 16-year NFL career. And every time, he wanted to keep playing. Most of the time he did.

But now, new rules require more extensive testing before a player is cleared to return to the field.

"The biggest thing we want to see from a medical standpoint is that the symptoms of the concussion go away," says Dr. Eric Warren, medical director of the Novant Health Sports Medicine Center.

Warren says the most common symptoms are headaches and dizziness. Other complications include vision problems, memory loss and stability challenges.

Warren says most players return to the field in three weeks or less. But Newton's concussion may have a complicating factor: he just suffered multiple hits, including a hard helmet-to-helmet impact in the season opener against the Denver Broncos.

"One thing we want to avoid is having head injuries and concussions that build on each other," Warren says.

He says back-to-back hits in a short period of time can compound the effects of a concussion and lengthen recovery time.

At a news conference Monday, Panthers head coach Ron Rivera didn't have answers about Newton's status.

"I don't want to say something that could go against what the trainers are saying-- or the doctors, for that matter."

Warren says there is a simple saying he uses with every player, parent and coach: "When in doubt, hold them out."