Baltimore Ravens offensive lineman John Urschel surprisingly retired from the NFL on Thursday at the age of 26. 

According to CNN's Jill Martin, Ravens head coach John Harbaugh was informed of the decision on Thursday and released the following statement on Urschel: "We respect John and respect his decision. We appreciate his efforts over the past three years and wish him all the best in his future endeavors."

Urschel released a statement on the decision:

A source told ESPN's Jamison Hensley that the results of a recent chronic traumatic encephalopathy (CTE) study played a role in Urschel's retirement.

Urschel is pursuing his doctorate at the Massachusetts Institute of Technology.

The aforementioned study was published Tuesday in the medical journal JAMA (h/t CNN.com's Daniella Emanuel). Doctors discovered CTE in 110 of 111 brains from deceased former NFL players.

Urschel is a mathematician, and he said the head trauma after a 2015 concussion impacted his ability to think, according to Hensley: "I think it hurt my ability to think well mathematically. It took me about three weeks before I was football-ready. It took me a little bit longer before my high-level visualizations ability came back."

The Ravens selected Urschel in the fifth round of the 2014 NFL draft out of Penn State. The team utilized him primarily as a backup guard, although he also made appearances at tackle and center. He made 13 starts during his three-year career.

Prior to his retirement, Urschel was in the mix for Baltimore's starting job at center. Ryan Jensen and Matt Skura will now compete for the spot.