It has been six months since the doctor behind one of the most daunting studies of the NFL's concussion problem challenged the NHL to step up its own research of head injuries. And while there hasn't been much, if any, follow-up from NHL commissioner Gary Bettman, there most definitely has been from former NHL players.

Just one special on HBO's "Real Sports with Bryant Gumbel" this week made that clear.

Investigating the link between hard hits in hockey and chronic traumatic encephalopathy (CTE), the degenerative brain condition that has  rocked the NFL, the show featured commentary from a number of ex-pros, including Hall of Famers Ken Dryden and Eric Lindros. And the consensus was that the NHL can do more to either acknowledge the reality of CTE or at least make efforts to overcome it.

"We can do better," said Lindros, whose prestigious career has now become synonymous with concussions. “(Explicit) yeah, we can. We can do a lot better."

Even more outspoken was Paul Montador, the father of late NHL veteran Steve Montador. After talking about his son's sudden death at the age of 35, which followed a concussion-riddled 10-year career in the NHL, he was asked for his response to Bettman, who, per HBO, still takes "the public position that there is no link between hockey and its head hits and CTE."

After a long pause, Montador gave his response: "The Earth is flat."

"Critics charge that in failing to admit the game has a problem, the league's leadership has also been slow to reform rules and policies that would protect their players," the HBO special detailed, "while about 150 former pros have filed a lawsuit against the NHL for failing to protect them from head injuries."