DS Penske driver Vergne was considerably low on energy in the final stages of the 33-lap contest compared to Envision's Cassidy, who kept the pressure up on him in a bid to take only his second career victory in FE.
But Vergne covered off the inside line into the Turn 3 hairpin - the primary overtaking point of the race - on every lap since a late safety car period triggered by McLaren's Jake Hughes, preventing Cassidy from making a move.
