During his opening statement, an attorney representing the university, Alex Barbour, challenged the notion the players are employees. He said academics are at the center of a football player's college experience.
"Academics always trumps athletics at Northwestern," he said. "Northwestern is not a football factory."
During his testimony, Colter said he abandoned his hopes of entering a pre-med program because of time demands Northwestern makes on football players. He said chemistry was invariably offered at times that conflicted with football practice.
"You fulfill the football requirement and, if you can, you fit in academics," he said. "You have to sacrifice one, But we can't sacrifice football. ... We are brought to the university to play football."
Devoting more time to academics at the expense of his football, he added, could result in the loss of a scholarship. Asked if coaches ever told players to leave practice and go study, Colter said no.
Another Northwestern attorney, Anna Wermuth, asked Colter whether playing football was, in itself, part of the education process. Does it help players learn to "critically analyze information?" she asked.
"We learn to critically analyze a defense," said Colter, who ended up studying psychology. Football also taught values, including perseverance, he added.
"But that does not mean it helps you earn a psychology degree," he said. "It makes it harder."
Colter said most of the team's 85 scholarship players support forming a union, though he has been the only one to step forward publicly with the support of the Steelworkers, the players association and its leader, former UCLA linebacker Ramogi Huma.
Supporters say a union would provide athletes a vehicle to lobby for financial security and improved safety, noting that players are left out of the billions generated through college athletics. They contend scholarships sometimes don't even cover livings expenses for a full year.
University attorneys are expected to call their own witnesses later in the week. A decision by the NLRB could come soon after the testimony concludes.
For now, the push is to unionize athletes at private schools, like Northwestern. Public universities, which are subject to different regulations, could follow later.