Grantham was named Louisville's defensive coordinator on Sunday. He was the second defensive assistant to leave Georgia. Secondary coach Scott Lakatos resigned on Thursday, citing undisclosed personal reasons.
Under Grantham, Georgia's defense produced mixed results.
In 2011, the Bulldogs ranked fifth in the nation in total defense. His 2012 defense was packed with talented players, sending seven players to the 2013 NFL draft, but was perceived as underachieving.
Grantham had to rebuild the defense in 2013, when Georgia ranked only eighth in the Southeastern Conference in total defense and 78th in the nation in scoring defense. Georgia gave up 29 points per game to rank 78th in the nation as the Bulldogs finished 8-5.
Georgia did not announce if Pruitt will coach defensive backs at Georgia. Pruitt is scheduled to meet with reporters in Athens on Wednesday.
The signature play of the 2013 season for Georgia's defense came in the Bulldogs' 43-38 loss to Auburn. Nick Marshall's 73-yard pass was deflected by Georgia defensive back Josh Harvey-Clemons and then caught by Ricardo Louis for the go-ahead touchdown with 25 seconds remaining.
The Associated Press contributed to this report.