The Video Assistant Referee (VAR) was called to duty in the opening French Ligue 1 game of the season, and Cesc Fabregas was the culprit.
Monaco went one goal down, no thanks to a Moussa Dembele's 5th minute strike, before Fabregas was sent off at the Stade Louis II.
The midfielder had originally been shown a yellow card for a foul on Leo Dubois but the decision was referred to VAR.
Replays showed Fabregas had raked his studs down the back of Dubois' leg and the card was upgraded to red in the 30th minute.
Six minutes later, Memphis Depay doubled the score for Lyon when goalkeeper Benjamin Lecomte, making his debut after signing from Montpellier, let a long-range effort deflect in off his legs.
Lucas Tousart drilled in from outside the box with ten minutes remaining, to hand Lyon a bright start away from home.