The counterclaim accuses Pastner of "sexual assault, sexual battery and intentional infliction of emotional distress" when Pastner was the head coach of the University of Memphis men's basketball team in 2016.
The lawsuit details an alleged incident in which Pastner reportedly attempted to force Pendley to perform oral sex on him, and Pastner allegedly told Pendley he would make her life "a living hell" if she ever mentioned the incident.
In a statement Thursday, Pastner's attorney called the counterclaim "false and malicious."
"There was no sexual assault. It is a lie. Josh never acted improperly with Ms. Pendley. Never," Pastner's attorney, Scott Tompsett, said in his statement.
The 40-year-old Pastner is the current head coach of Georgia Tech's men's basketball team. He played for UA under then-head coach Lute Olson from 1996-2000 and was a member of the Wildcats' 1997 national championship team. He served as an assistant coach at UA under Olson from 2002-08.
Pastner was an assistant coach at Memphis from 2008-09 before being promoted to head coach, a position he held at Memphis from 2009-16 before taking the head coaching job at Georgia Tech.
Pastner filed a defamation lawsuit against Bell and Pendley in January, two months after Bell told CBS Sports that he had provided extra benefits to a pair of Georgia Tech players. The claim was later confirmed to be true, but Pastner said he had no knowledge of those benefits.
In January, CBS Sports' Gary Parrish reported Pastner's attorneys claimed Bell and Pendley told investigators that Pastner had assaulted Pendley. "Pastner emphatically denied that allegation, reported it to law enforcement officials and filed the (defamation) lawsuit," Parrish wrote.
"I am disgusted and devastated by the actions of two individuals to whom I showed compassion," Pastner said in a statement after filing the defamation lawsuit in January. "My family and I are victims of fraud and extortion and the extent to which these individuals have gone to harm us is truly unfathomable. I absolutely and unequivocally never assaulted or harassed Ms. Pendley, and I am truly sickened by these false claims."