Nassar is currently serving 40 to 175 years in prison for sexually assaulting more than 150 women and girls while serving as a doctor for Michigan State University and Team USA gymnastics.

According to court docs filed by his public defender, Jacqueline McCann, Nassar was assaulted within hours of being released into the general population back in May at the United States Penitentiary in Tucson, AZ.

Nassar apparently suffered injuries in the attack -- but the details surrounding the incident are unclear at this point.

Interestingly, Nassar's attorney is accusing the judge in his criminal case of essentially inciting the violence -- claiming the way she oversaw the proceedings empowered inmates to attack him.

McCann references specific quotes from the hearing in which Judge Rosemarie Aquilina "proclaimed, with apparent relish, that she was signing his 'death warrant.'"

In court docs, McCann says, "Unfortunately, Judge Aquilina's comments and conducting of the sentencing proceeding appeared to encourage this type of behavior."

Now, it seems Nassar could be moved to another prison.