Jeff Gordon can admit it now. Even with the sweeping changes in how sports treats head injuries, Gordon had never heard of the standard test that offers a tangible measure of what's going on in the brain after a concussion.

Dale Earnhardt Jr. made Gordon aware and put NASCAR on notice that the way drivers deal with concussions is as outdated as the Car of Tomorrow. Long a favorite pitchman as NASCAR's most popular driver, Earnhardt's weighty plug to his fellow drivers these days: Don't ignore or hide the troubling symptoms of a concussion, and take an ImPACT test to aid in recovery.

"This test can pinpoint where in the brain you're struggling, what kind of injury you have, what kind of things you can do to rehab and to recover," he said. "It helped me a lot. There was a lot of good information I learned throughout that whole process."

Gordon, his Hendrick Motorsports teammate, listened and voluntarily took a baseline concussion test before the start of the season.

"I just think whether it's voluntary or not, it's a good idea to have," Gordon said. "I don't think that NASCAR necessarily has to make it mandatory, but if you're a race car driver, and you feel you're going to be here for a while, you need to make it mandatory to yourself."

Gordon was ahead of the game. NASCAR appears set to make baseline concussion tests mandatory for all drivers in 2014.

Steve O'Donnell, NASCAR's senior vice president of racing operations, said officials had already urged drivers to take an ImPACT test before this season. It's a critical move in a sport where brutal blows to the head are always a risk with every 200 mph wallop into a wall.

O'Donnell said NASCAR had identified 32 concussions in their top three national series since 2004, including three last season. The one suffered by Earnhardt forced NASCAR concussions right into the spotlight.

He was injured in a crash during an August tire test at Kansas, but didn't seek treatment for the mild concussion. His stubborn streak instead kept him behind the wheel. He was then part of a 25-car pileup in October at Talladega that triggered lingering headaches and other recognizable warning signs.

Earnhardt went to a doctor, and he was ultimately benched for two races. His drive for his first Cup title was dashed.

In the 12 years since his father's death at Daytona, NASCAR introduced a series of measures designed to keep their drivers safe, from helmet and restraint systems to impact-absorbing SAFER barriers along their concrete walls, all designed to cushion the blows of high-impact accidents.

ImPACT testing is only the latest step in bolstering driver safety. But winning over the entire field with real proof that testing works and that putting the final decision in taking the seat in the hands of doctors is the right call will take time.

Mark Martin said he won't let doctors call the shots on when he races.

"Let's say I tripped on a banana peel and broke my thumb," he said. "If I want to drive my race car with a broke thumb, there's no reason why I shouldn't be able to. I'd rather be the one making decisions. It would scare me to death if somebody told me, 'You can't do that.'"

Jeff Burton, one of the field's most respected drivers, wanted to learn more about the test before endorsing NASCAR's use.

"I think nobody wants to drive in a condition they shouldn't drive in, but I think we all feel like we are our own best judge to determine if we should drive or not," he said. "So, the interpretation of the results, I think, is the biggest concern."

Dr. Mark Lovell developed the ImPACT test now used by many professional sports leagues, including the NFL, and has tested several NASCAR stars for years. He said false positives are rare and could happen in any kind of medical test. If the score is low, and the driver voiced concerns, he could retest. Plus, ImPACT is only one factor in determining recovery from a concussion. There are checks for everything from balance, to the brain's reaction to physical activity.

NASCAR said flunking the test alone will not keep a driver out of a race.

"We've got a select group of neurologists and it's going to be their call," O'Donnell said. "We don't think that should be us. We think it should be someone that specializes in that field."

Some of the sports greats from earlier eras are forced to deal with the fact they likely raced at dangerous speeds with a serious head injury.

"I think I drove more with a concussion than I did without one," seven-time Daytona 500 Richard Petty said, laughing.

The Hall of Famer driver turned serious as he applauded NASCAR's dedication to safety, and called Earnhardt smart to sit out.

Michael Waltrip labeled the 1980s and 1990s the most dangerous era in the history of NASCAR. He said he was knocked unconscious or knocked silly dozens of times over the course of a 30-year career that includes two Daytona 500 wins. With dark humor, he recalled simply running across the track after his car clobbered the call, and waking up the morning after one serious hit at his mother's house, with no idea how he got there.

"Back then, if you said you were OK and you could hold up two fingers, you could pretty much go in your car and go home," Waltrip said.

And now?

"You wouldn't be able to leave the track," he said.

NASCAR says if drivers are unable to drive their car back to the garage after an accident, they have to make a mandatory trip to the infield care center. The attending physician could then refer a driver to a neurosurgeon for a CT scan or MRI if they suspected a concussion. Clearance to race after suffering a concussion is not given until after a driver obtains a medical release.

"We have our own hospital at every track which, I think, is unprecedented," O'Donnell said.

The premature deaths and degenerative brain ailments reported in former NFL stars and NHL enforcers have made athletes in all sports more aware of the frightening consequences of trying to tough it out and compete with a concussion.

"I told my buddy the other day that I feel fine, but if y'all start to see me think I might go somewhere and hurt myself, go with me," Waltrip said. "I'm pretty sure I'm OK. I don't want to wander off and do something dumb. You don't know how those things affect you."

For all the praise Earnhardt received for scheduling a doctor's appointment, it was only after he was all but eliminated from championship contention. With so much at stake — from wins to sponsor commitments to hefty purse money — drivers have every incentive to hide an injury.

Yes, Earnhardt sought medical attention. Yes, Gordon endorsed baseline testing and sitting out to heal the brain.

But inside the head of every driver is the ability to mentally shake off the life-altering consequences ahead all because of one pileup or blown tire — even if that includes sliding into the cockpit with a concussion.

"If I'm a race car driver," Waltrip said, "I'd still try to fake it."


Follow Dan Gelston online: https://twitter.com/APGelston and http://racing.ap.org