Looks like that prediction was a day late.
From today's Chicago Tribune:
Of 21 high school players monitored for a full season by a team of researchers from Purdue University, four players who were never diagnosed with concussions were found to have suffered brain impairment that was at least as bad as that of other players who had been deemed concussed and removed from play.
"They're not exhibiting any outward sign and they're continuing to play," said Thomas Talavage, an associate professor at the Weldon School of Biomedical Engineering at Purdue and the lead researcher on the study. "The cognitive impairment that we observed with them is actually worse than the one observed with the concussed players."
The report, published in the latest edition of the Journal of Neurotrauma, found that some players received more than 1,800 hits to the head during practices and games, some with a force 20 times greater than what a person would feel while riding a roller coaster.