By Jon Herskovitz
(Reuters) - A Baltimore Ravens offensive lineman pursuing a doctorate in mathematics announced his retirement from football on Thursday, and team officials reportedly said a new study linking NFL players to brain disease was a factor in his decision.
John Urschel, 26, a Ph.D. candidate at the Massachusetts Institute of Technology who has been dubbed the "smartest player in the National Football League," called Ravens Coach John Harbaugh and said he was retiring, Harbaugh told a news conference.
"That was something that’s been on his mind for quite a while, throughout the off-season," Harbaugh said, adding that Urschel's decision had surprised him.
Urschel, who spent all of his three professional seasons with the Ravens, said in a statement on Twitter that he was excited to be a working full time on his doctorate. He also said he and his fiancee are expecting their first child in December.
"It wasn't an easy decision but I believe it was the right one for me. There's no big story here and I'd appreciate the right to privacy," Urschel said.
His statement did not mention concerns about injury or a study released this week on chronic traumatic encephalopathy, or CTE, a debilitating brain disease linked to head injuries, but the Baltimore Sun cited team sources indicating his decision was related to the study.
The report in the Journal of the American Medical Association said the brains of 99 percent of former NFL players studied showed signs of CTE, which can lead to aggression and dementia.
Urschel, a 6-foot, 3-inch (1.9 m), 300-pound (136 kg) player who joined the Ravens from Penn State University, is studying applied mathematics at MIT. He was the co-author of a research paper titled "Spectral Bisection of Graphs and Connectedness" that was published in 2014, the same year he began his professional football career.
An avid chess player who reads math books to relax, Urschel was featured in a television commercial in which he explains the technology behind noise-cancelling headphones to J.J. Watt, a star player for the Houston Texans, who uses the technology to tune out the lecture.
In a 2015 article he wrote in The Players' Tribune, Urschel said he loved playing football and accepted the risk of brain injury.
"Objectively, I shouldn’t. I have a bright career ahead of me in mathematics," he wrote, adding that he was not seeking to get rich playing football.
"The things I love the most in this world (reading math, doing research, playing chess) are very, very inexpensive," he wrote.
(Reporting by Jon Herskovitz in Austin, Texas; Editing by Dan Grebler and Bill Trott)