One of the N.F.L.’s smartest players did the math and decided to retire after just three years in the league.

John Urschel, an offensive lineman for the Baltimore Ravens who received much publicity for his off-season pursuit of a doctorate in math at M.I.T., told the team on Thursday that he was hanging up his cleats at 26.

Urschel’s agent, Jim Ivler, said Urschel was overwhelmed with interview requests but would not be speaking to the news media. On Twitter, Urschel wrote that “there is no big story here” and that the decision to retire was not an easy one to make, but “it was the right one for me.”

He added that he planned to return to school full time in the fall, “to take courses that are only offered in the fall semester” and spend time with his fiancée, who is expecting their first child in December.

Urschel’s decision came two days after the release of a study in which all but one of 111 brains of former N.F.L. players showed signs of chronic traumatic encephalopathy, a degenerative brain disease linked to repeated hits to the head.

Continue reading . . .