Kyle Kennedy, who blew the lid off his relationship with the late NFL star while serving a sentence with him at a prison in the Souza-Baranowski Correctional Center in Lancaster, Massachusetts, revealed in an Instagram post that he hit a car on his street bike and broke his spine in three places.
He had to undergo a seven-hour long back surgery and recovery is expected to take a long time, OK! has been told.
The highly controversial Kennedy was released from jail last year.
Kennedy — also known as “Pure” — drew several media headlines after he spoke out about Hernandez for the first time on TV.
He told REELZ the late New England Patriots tight end was "the most loyal person" he had ever met and that they used to do everything together — cook food, smoke, listen to music, get high, and "just chill".
He had added that they didn't want to be around other people and that they "used to write letters back and forth to each other all day."
Now-hospitalized, Kennedy had also revealed that he and Hernandez even sold and did drugs every day.
Kennedy was the primary source in journalist Dylan Howard's 2019 book Aaron Hernandez's Killing Fields. In the book, he spilled beans on his former cellmate, stated that Hernandez had claimed ties to a fourth murder.
"Hernandez always used to tell me he had four murders," Kennedy had told journalist Dylan Howard for his book.
"He would just always, all the time joke around saying, 'I got four bodies."
Hernandez was at the peak of his career in 2012 after his team offered him a five-year contract extension. His $12.5 million signing bonus happened to be the largest amount ever given to a tight end in the NFL.
On June 18, 2013, Hernandez was arrested for the murder of Boston Bandits linebacker Odin Lloyd who was dating the sister of Hernandez's fiancé. The motive for the murder wasn't quite articulated during the trial, but the prosecutors said that it was over something trivial.
The Patriots team released him 90 minutes after he was charged with murder. While being probed for Llyod's murder, he also faced trial for the double murder of Safiro Furtado and Daniel de Abreu in 2020.
Ultimately, the former tight end was acquitted for the double-murder but was sentenced to life in prison for the murder of Lloyd.
In 2017, he hanged himself behind bars. He was 27 years old.