He doesn't always actually wear the mouthpiece. The semicircle of fitted plastic sometimes dangles from his bottom lip as Gerald Wallace glides down the court for the Charlotte Bobcats and his molars chomp one of the gnawed ends, or he will push the protection forward until it protrudes well in advance of his front teeth, looking like a bumper.

But he does have one every game. Doctor's orders.

This is four concussions later, all within about four years, all after going from the Kings to the Bobcats in the 2004 expansion draft. Wallace knows he must use the mouthpiece as one of the few preventative measures available to avoid No. 5. He knows his mother has grown concerned about what the mounting number of brain traumas will mean for him later in life.

"But that's what moms are supposed to do," Wallace said. "They're supposed to worry. But other than that, everyone is pretty calm."

Wallace himself. The Bobcats. Other teams. NBA officials.

Amid an inexplicable rash of concussions, and with experts saying Wallace and others with multiple incidents could be at greater risk for health issues later in life, the league says it is monitoring the situation but has not charted an increase or decrease in cases. Wallace said he is not concerned. Orlando's Jameer Nelson, who has had three, said he is not concerned.

But everyone just went through some two weeks.

• Jan. 16: Marvin Williams of the Hawks, after a blow across the forehead from the Warriors' Ronny Turiaf, fell and suffered a concussion when his head bounced off the court. He shot two free throws, left the court, soon after vomited in the locker room and spent the night in an Oakland hospital for observation. He later told the Atlanta Journal Constitution he did not remember throwing up.

• Jan. 25: Brian Scalabrine of the Celtics was struck inadvertently in the face by the Mavericks' Dirk Nowitzki and left with a concussion.

• Jan. 27: Scalabrine returned to practice, got hit in the head by teammate Patrick O'Bryant while going for a rebound and again sustained what coach Doc Rivers termed a mild concussion. Scalabrine did not play again until Feb. 19.

• Later Jan. 27: The Lakers' Trevor Ariza, defending Wallace of all people, slammed into a screen by the Hornets' Juwan Howard and left with a concussion that prompted dizziness, nausea and ringing of the ears. He played the next game three nights later - and only then revealed he also might have suffered a concussion Jan. 22 against the Wizards in a collision, though the exact nature of the injury was not diagnosed. Coach Phil Jackson told the Orange County Register he found the situation a "little concerning."

"I don't know if guys had harder heads or if we didn't jump as high," said Del Harris, who has been on an NBA bench as a head coach or assistant since 1976 and currently serves on Vinny Del Negro's staff with the Bulls. "Either one is possible. But there was not the kind of frequency that we've been having lately with that. Having said that, a lot of times, injuries tend to run sort of in cycles for some reason"

League officials say it is just that, a momentary cycle.

But Dr. David Hovda, the director of the UCLA Brain Injury Research Center, noted what is at least a temporary increase and said, "As pro athletes become quicker, faster and stronger, I am not surprised. I am not surprised that there have been a number of concussions in the National Basketball Association."

Hovda added, "When I hear that a player has had four of them or five or six, I honestly always double that number. They have usually also had some before or in practice or in pickup games."

No known studies track concussions in basketball players, professional or amateur. When Wallace suffered his fourth such trauma, last season against the Kings after being accidentally hit in the face by Mikki Moore, the Bobcats' medical staff, searching for insight, consulted the NFL's Carolina Panthers on how they cared for linebacker Dan Morgan, who had five recorded concussions.

Call The Bee's Scott Howard-Cooper, (916) 321-1210.