Gary Neville watched his Valencia team slide into the Europa League after his Mestalla debut saw Lyon claim a 2-0 Champions League victory.
The former Manchester United defender succeeded Nuno Espirito Santo last week and, after being absent for Saturday's Primera Division draw with Barcelona, took control of Los Che for the first time on Tuesday night.
The Valencia faithful packed out the Mestalla to see how their new English boss would fare in his maiden assignment and the early signs were promising, with Rodrigo De Paul setting up Shkodran Mustafi for an early header that hit a post.
Cornet bit back for Lyon, the Ivorian forcing a parried save from Jaume Domenech in the 11th minute.
Valencia's goalkeeper kept out Rafael -- the right-back who succeeded Neville as right-back at Old Trafford -- before Paco Alcacer's header drew a smart stop from Anthony Lopes at the other end.
Cornet drove home a fine goal from fully 20 yards out to make the breakthrough in the 37th minute and Neville, assisted by his brother Phil, began to look nervous on the Mestalla touchline.
After the break Valencia tried their luck through substitute Javi Fuego and full-back Joao Cancelo, who both worked Lopes with drilled efforts, but Lyon were unabashed and urged Sergi Darder forward to send Domenech sprawling in the 71st minute.
Within five minutes Lyon had doubled up, Lacazette pinging the ball into the bottom corner from distance.
Aymen Abdennour did have an opportunity to drag Valencia back into the tie with his headed attempt but with Gent beating Zenit 2-1, the Spaniards' fate was out of their own hands.