Williams, a former star at Strong Vincent High School in Erie, played in 10 games in 2007, catching five passes for 100 yards and a touchdown.
Williams was expected to be Pitt's top deep threat this season, and his absence will create an opening that could be filled by incoming freshman receiver Jonathan Baldwin of Aliquippa.
Williams plans to remain on Pitt's team and take a redshirt season. He would have three seasons of eligibility remaining.
"We believe Maurice can achieve a lot at Pitt, both academically and athletically, and our expectations are for him to use this as motivation for improvement," Panthers coach Dave Wannstedt said in a statement.