MONTREAL — In a black gown and a red tie, Laurent Duvernay-Tardif looked at ease making small talk with fellow graduates here as he waited to be called up to the stage to receive his degree. His name was announced, dozens of cheers erupted and a moment eight years in the making was finally complete: The Kansas City Chiefs guard was now the N.F.L.’s first active player to become a medical doctor.
After the ceremony, Tuesday morning on a hill in a city 335 miles from the nearest N.F.L. team, Duvernay-Tardif put on a white lab coat with his red Chiefs No.