Defender Youssouf Kone was sent-off for a headbutt as Lyon lost 1-0 to Montpellier in Ligue 1 on Tuesday, in Sylvinho's first defeat in charge.
Kone was sent off early in the second half after clashing heads with the home side's Algeria international Andy Delort.
Before the defeat, coach Sylvinho had guided the side to convincing wins over Monaco and Angers in his first two Ligue 1 matches in charge.
Montpellier claimed their opening win of the season with right back Arnaud Souquet's wonderful half-volley shortly before the break.
The fixture had been moved, along with two other games, from the weekend to free police resources for the G7 summit taking place in Biarritz in France's south-west.
"We had a lot of chances. Even if the red card changed things a little we managed the second half well. We could have killed the match off," goalscorer Souquet said.
"For the goal, I hit the ball as it came. When the ball left my foot I told myself there was a good chance it would end in the back of the net," he added.
The hosts dominated the early play at Stade de la Mosson with forward Delort wasting a good chance after 15 minutes.
Delort, an African Cup of Nations winner during the summer, had a chance to claim an advantage a quarter of an hour later.
Denmark youth international Joachim Andersen tripped Delort in the box. The bleach-blonde forward took the spot kick, but hit the post.
Montpellier took the lead with three minutes of the first half remaining.
Lyon left-back Kone headed a Florent Mollet corner away but Souquet met the clearance on the half-volley. His shot flew high into the net untouched with goalkeeper Anthony Lopes flat footed.
Kone's match went from bad to worse six minutes into the second-half when he was shown a red card after a clash with Delort off the ball.
Lyon captain Jason Denayer had a chance to bring the side level but his header from Bertrand Traore's free-kick only found the side netting.
With five minuted play, Delort's chipped effort beat Lopes and also the cross bar.
On Wednesday, in the remaining early games of the round, Nice, fresh from a takeover by English billionaire Sir Jim Ratcliffe, host Marseille, looking for their first league win under Andre Villas-Boas, while Lille host Saint-Etienne.