Wesley Fofana showed why Brendan Rodgers expects him to become a world star by returning from injury to score his first Leicester goal and seal a place in the last eight of the Europa Conference League.
The French defender had not played since breaking a leg and damaging ankle ligaments in an August friendly with Villarreal, but he crowned a superb display with the decisive goal early in the second half of a game that threatened to boil over.
Rennes boss Bruno Genesio and Leicester midfielder Kiernan Dewsbury-Hall were booked after the final whistle and players had to be separated by stewards when substitute James Maddison riled his opponents with wild celebrations.