Maxwel Cornet's slick early strike was followed up by a wonderful individual goal from Sergi Darder just before the interval, with Lucas Moura's second-half goal not enough to spark a comeback in a 2-1 loss that ends an undefeated league sequence which started back in March 2015.
Blanc conceded the defeat came out of the blue for him and his squad, but wants them to use the result as motivation for the rest of the campaign.
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Blanc, whose side lead Chelsea 2-1 in Europe after the first leg, said: "A wake-up call is exactly what I have told the players. To win in a wonderful stadium it is not enough just to stand there.
"We go to Saint-Etienne on Wednesday and this will give them ideas. I hope we will not show the same face as we did here. The mentality, aggressiveness and desire was gone from us, but we did get it for 36 matches.
"I hope we will remobilise for the future. We beat the record anyway and that will always be there.
"Lyon deserved to win – they had the technical quality and the aggression to get there. They were in the best of moods.
"But if I had an explanation, I would give to the players – this game was totally unexpected. Nothing in our preparation suggested we would play so poorly. Were we too relaxed preparing? I don't know
"We must use this to regroup. We expected a difficult game, but not as hard as this. We were missing many things, including the mind-set and commitment required to win."