Opportunist goals by Ignatius Ganago and substitute Simon Banza gave Lens a 2-0 win at Monaco and piled the pressure on home manager Niko Kovac after both teams finished with 10 men in their Ligue 1 clash on Saturday.
The result provisionally lifted Lens up to fourth on five points from three games after their first league win of the season while Monaco dropped to 17th with one point following a second successive defeat.
With one eye on Wednesday's Champions League playoff round return leg at Shakhtar Donetsk, where Monaco aim to overturn a 1-0 first-leg deficit, Kovac fielded a makeshift side as he left several regular starters on the bench.
Ganago fired Lens into a 51st-minute lead when he robbed Strahinja Pavlovic of the ball and powered his shot past Alexander Nuebel, as the home side's stand-in keeper got a hand to the ball but could not keep it out.
Lens had Cheick Oumar Doucoure red-carded on the hour for a studs-up challenge on Krepin Diatta before Monaco's Russian forward Aleksandr Golovin followed in his footsteps in the 85th minute for a rash tackle on Banza.
The late substitute sealed his team's victory after another calamitous defensive error by Monaco, with left back Caio Henrique giving the ball away to Przemyslaw Frankowsk who squared the ball to Banza for a simple finish.
In the day's other fixture, champions Lille visit St Etienne looking for their first win of the season after collecting one point from their opening two games.