Luuk De Jong's 87th minute strike on Wednesday meant Spurs are now on the edge of a Champions League exit and Dembele knows his team must kill games off better.
However despite their struggles in Europe, domestically Tottenham have made their best start to a Premier League season and go into the mouthwatering clasg at Wembley only two points behind the champions.
The magnitude of the game is not lost on the Belgian midfielder: “Obviously it’s an important game – everyone knows how important it is,” he said.
“For us, we know it’s just as vital as any other game, so we need to be focused to try to get the win.
“Everyone will be very motivated to play against them and I think this could be an important game for both teams’ seasons.”
“I think we are doing well this season in the Premier League, but we have to finish games off much more quickly,” admitted the former Fulham man.
“I think in the Premier League we are winning games and we need to continue in that spirit.”