Folston, the Fighting Irish's leading rusher last season (889 yards, six touchdowns), left Saturday's 38-3 win over Texas during Notre Dame's second drive and did not return. He is scheduled to undergo surgery in the next 10 days, Kelly said.
Kelly said the injury was to Folston's MCL, but Notre Dame later clarified that the junior had torn his ACL.
Redshirt junior C.J. Prosise and freshman Josh Adams took the bulk of the carries in Folston's place. Prosise had 20 rushes for 98 yards, while Adams carried the ball five times for 49 yards with two touchdowns.
The loss of Folston hurts an already thin position for the Irish, who lost reserve running back Greg Bryant this summer due to academic shortcomings. Prosise had been converted from receiver during the spring, a move that has proved beneficial for the depleted backfield. In addition to Adams, freshman Dexter Williams could see some extended time.
No. 11 Notre Dame travels Saturday to Virginia.