It was no big deal, said University of Maryland football player Devonte Campbell. The tight end remembers catching a short pass in a practice scrimmage last month, lowering his shoulders as he turned downfield, and ramming helmet-to-helmet with an oncoming defender.

"I had a nice little headache," the third-year player said with a smile. "It wasn't intentional, you know. Just happens from playing the sport."

It happens a lot. As Maryland and Navy begin their seasons today at M&T Bank Stafium — renewing a 105-year-old rivalry — the public's focus will naturally be drawn to the game's most jarring tackles. But it is the gentler but still potentially damaging collisions, some on the practice field, that are attracting increasing attention from researchers and sports leagues. In the past year, the NCAA and NFL have adopted new measures to ensure that players with concussion symptoms are kept off the field.

This is the first season in which ACC officials on the field will be required to sideline players who appear disoriented or display other worrisome signs. Some connected to Maryland football are asking if the league is pushing its concern too far.

Maryland head coach Ralph Friedgen said he understands the increasing focus on concussions, but also worries that the 12-school conference's approach could have unintended consequences on the playing field.

"I'm not really fond of that rule because what if the official is not right — they take out your best player at a key time in the game [and it's] a major factor in the game," said Friedgen, 63, who has been in coaching for nearly 40 years. He said he hoped — and assumed — that the rule would be applied fairly and correctly.

Friedgen's anxiety is shared by Darryl Conway, an assistant Maryland athletic director for sports medicine. "That's kind of our worry. What if it's just a kid that's tired that's staying down longer? I understand the safety issues. But most concussions aren't apparent. They come to us the next day."

Apprised of Maryland's concerns, ACC associate commissioner Michael Kelly replied: "I can understand that. I don't think [the officials] will be overly focused when there is not a true issue there."

A Johns Hopkins neurocritical care doctor said the the rule is sensible. "To give the officials this authority is very appropriate if a player is showing neurological changes," said Dr. Robert D. Stevens. "The reason why is that the player's judgment may be impaired. It makes sense to have an independent person make that decision for you. For a long time there has been a culture of a tough guy who can withstand anything, and that needs to change."

Johns Hopkins Medicine recently directed an NFL-sponsored, head-injury conference in which Stevens was a participant. Stevens and others at Hopkins are concerned about the short-term effects of single hits and the long-term impact of multiple head blows. "The criteria we use for concussions may just not be sensitive or specific enough to detect some of the impacts people just brush off," Stevens said.

Campbell was diagnosed with a concussion and missed a week of practice. "Watching the tape — who knows with concussions? — he didn't really to me get hit hard," Friedgen said.

Within days, wide receiver Torrey Smith stumbled in practice and was hit in the head by a trailing player's knee. Maryland athletic trainer Wes Robinson "came up to me after the scrimmage and said, 'Torrey, he don't even know where he is. I don't know if he has a concussion or whatnot,'" Friedgen said. "Later that night, he was fine — he didn't have any symptoms" and was able to return after some rest, the coach said.

There was no specific label for Smith's injury. It fell into the vast expanse of head blows that defy characterization.

"He just got hit," Conway said. "We're not classifying it as one thing or another. "

Former Maryland quarterback Jordan Steffy said such injuries — physicians sometimes refer to them as "sub-concussive events" — are common.

"The thing that's so difficult is it's not a black and white thing," said Steffy, whose career ended in 2008 and who helps run a Pennsylvania foundation that aids at-risk kids. "Have there been times when I've taken a hit and the lights go out for a second? Sure. Is that a concussion? There are gray areas. A lot of guys continue to play. Certainly I did, too."

Steffy said he endured two serious concussions at Maryland, and two in high school. In 2007, Rutgers safety Joe Lefeged flung himself at the quarterback, hitting Steffy with an unnerving, helmet-to-helmet crack. Removed from the game, Steffy walked haltingly up the locker-room stairs and remained forgetful and occasionally disoriented for several weeks.

Despite his history of concussions, Steffy opted to return for another year in 2008 while enrolled in Maryland's real estate-development graduate program. He missed most of the season after fracturing his right thumb.

Today, he is headache-free but said his memory recall occasionally seems slow. "It's enough to be annoying," said Steffy, who believes the lapses may be related to his concussions.

Johns Hopkins psychiatrist Constantine Lyketsos said during the NFL conference in June that the research on repeated football head injuries is slim. "We have a sense of how often football players — whether professional or college — get concussions," he said in an interview on the medical school's website. "We don't have a strong sense of how often they actually get head injuries, and there is some evidence to suggest that head injuries can lead either to medium-term or long-term outcomes without necessarily causing symptoms that we call a concussion."

In imposing its new rule this season, the ACC said it wanted to be appropriately cautious.

"It is a point of emphasis for 2010," Rhoads said. Steffy called the rule "a step in the right direction" but said it may be hard to apply because concussions are so subjective.

As they seek to keep players safe, physicians say they often encounter resistance. Researchers at the NFL conference said many athletes still subscribe to a culture of sacrificing their bodies for the team — sometimes to the extreme.

Consider former Maryland player Danny Oquendo. Against Clemson a few years ago, the receiver and punt returner said "my body wasn't ready to stand up" after a hit in the back of the head left him dazed.

But Oquendo returned. He was "just woozy," he said, and was not diagnosied with a concussion.

"It looked like he could have a concussion because he got hit right in the back of the head," quarterback Chris Turner said at the time. "And then he was back in the game. That's just Danny."

jeff.barker@baltsun.com

Spotting Concussions

Doug Rhoads, coordinator of ACC officials, said the conference has made it a point of emphasis to sideline football players displaying concussion symptoms. Here, according to Rhoads, is some of what the officials will look for:

• "The first indicator is a headache, so obviously you can't see that," Rhoads said.

• Disorientation. "You might say, 'Do you know what quarter this is, which end zone is yours?'" Rhoads said.

• Slurred speech.

• Staggering.

• The NCAA also lists nausea, fuzzy vision and sensitivity to light or noise as concussion symptoms.