John Urschel, a Baltimore Ravens offensive lineman known for his passion for mathematics, has retired from the NFL at age 26.
In a statement released by the team, Ravens head coach John Harbaugh said Urschel had informed him of the decision Thursday morning.
"We respect John and respect his decision," Harbaugh said. "We appreciate his efforts over the past three years and wish him all the best in his future endeavors."
Urschel took to Twitter on Thursday afternoon with a statement.
"It wasn't an easy decision, but I believe it was the right one for me," Urschel said. "There's no big story here, and I'd appreciate the right to privacy."
Urschel earned Bachelor's and Master's degrees in mathematics from Penn State and is currently working on his PhD at the Massachusetts Institute of Technology (MIT), studying spectral graph theory, numerical linear algebra and machine learning.
In 2013, Urschel taught trigonometry and analytic geometry in the spring semester at Penn State and integral vector calculus during the fall semester. He also has had papers published, including one titled "Cascadic Multigrid Algorithm for Computing the Fiedler Vector," which appeared in the Journal of Computational Mathematics.
"I'm excited to start working on my doctorate in mathematics full time at MIT," Urschel said in Thursday's Twitter post. "I'm looking forward to the chance to take courses that are only offered in the fall semester, while spending time with my fiance and preparing myself for the new challenges that will come with fatherhood. We're expecting our first child in December."
In addition to his football and math talents, Urschel also is an aspiring chess master. He played chess against US champion Fabiano Caruana at the 2016 Genius Gala at the Liberty Science Center in Jersey City, New Jersey.
Urschel, listed in the Ravens team bio at 6 feet, 3 inches and 300 pounds, played college football at Penn State and was selected by the Ravens in the fifth round (175th overall) of the 2014 NFL Draft.
His retirement comes in the week a study published in the medical journal JAMA revealed that chronic traumatic encephalopathy, known as CTE, was found in 99% of deceased NFL players' brains that were donated to scientific research.
Urschel frequently wrote for the website The Players Tribune last season, focusing on math, statistics, football and player health and safety.
In the wake of Chris Borland's sudden retirement at the age of 24 in 2015 -- the former San Francisco 49ers player cited concerns over the long-term effects of repetitive head trauma -- Urschel wrote an article entitled 'Why I Still Play Football.'
"Objectively, I shouldn't," he wrote. "I have a bright career ahead of me in mathematics. I have the means to make a good living and provide for my family, without playing football. I have no desire to try to accumulate $10 million in the bank; I already have more money in my bank account than I know what to do with."
He later added: "I play because I love the game. I love hitting people. There's a rush you get when you go out on the field, lay everything on the line and physically dominate the player across from you. This is a feeling I'm (for lack of a better word) addicted to, and I'm hard-pressed to find anywhere else."
Urschel, who is from Buffalo, New York, played in all 16 of the Ravens' games last season, starting seven at center.