SAN FRANCISCO — An uninvited guest at the NFL’s pre-Super Bowl news conference about health and safety, Chris Nowinski listened Thursday as one of the league’s chief advisers about concussions declined to acknowledge a link between football and the brain disease called CTE.

“I wanted to see the talking points in real time, and you can tell it affected me emotionally,” said Nowinski, executive director of the Concussion Legacy Foundation and an outspoken critic of the NFL on the topic of head injuries. “It’s just incredibly frustrating to see this stuff.”

What he found particularly bothersome was an exchange between reporters and Dr. Mitch Berger, a member of the NFL’s head, neck and spine committee.

Berger would not draw a direct line from football to chronic traumatic encephalopathy (CTE), a disease linked to repeated brain trauma and associated with symptoms such as memory loss, depression and progressive dementia.

Berger, chair of the department of neurological surgery at the University of California-San Francisco, repeatedly said that while CTE have been found in late football players, such signs have also been found “in all spectrums of life.”

Tao, a protein that indicates the presence of CTE, “is found in brains that have traumatic injuries,” Berger said, “whether it’s from football, whether it’s from car accidents, whether it’s from gunshot wounds, domestic violence — it remains to be seen.”

Nowinski rejected that explanation.

““This is clearly part of a strategy to say, ‘Don’t focus on the fact that over 100 NFL players have been diagnosed with CTE in the last decade,” he said.