NFL players have become significantly larger over the last 30 years, which may cause more injuries, Will said on "This Week." Although there were only three NFL players who weighed more than 300 pounds in 1980, there were 352 in 2011, he said. Three of those players weighed more than 350 pounds.
"Repeated, small but repeated blows to the head, the brain floating in the pan in the skull, now we know causes early dementia and other problems," he said, adding that football will have to change from "down below" as parents refuse to let their children play a sport that could give them brain trauma.
Seau's death in May prompted NFL player Jacob Bell to quit the sport altogether, leaving behind his contract with the Cincinnati Bengals.
"We're getting so much money, so much glory, so much fame; we're boosting our egos so much by playing a sport that's violent and could later on risk our lives," Bell said in May.
CTE researchers from Boston University were unavailable, and do not comment on players' deaths until more research is obtainable.
The Associated Press contributed to this report.