Radamel Falcao has described Monaco's start to the season as "terrible" after a 2-0 defeat to Saint-Etienne on Friday extended their winless run in Ligue 1 to seven games.
Last year's runners up have endured a torrid start to the campaign, with an opening day win over Nantes their only maximum points return.
Two goals from Wahbi Khazri compounded their misery on Friday, with Colombian striker Falcao citing their inability to defend robustly enough as a primary cause of their struggles.
They travel to Germany on Wednesday to face Borussia Dortmund in the Champions League and the 32-year-old has demanded an improved performance from the team.
"It's not just against St-Etienne, it's a terrible start to the championship," he told Canal+.
"We have not managed to be as effective as expected and we have not been able to defend in the best way.
"We cannot go on like that, we have to raise our heads because on Wednesday we have to go to Dortmund to get a good result."