PSG defender David Luiz believes Chelsea are stronger without him.

PSG meet Chelsea in the Champions League next week.

Luiz believes Diego Costa has improved Chelsea and said: "He's perhaps the player they were missing: he balances the midfield, makes the team play well and knows how to hold on to the ball from time-to-time.

"With the arrival of Costa -- a warrior forward who always wants to score and challenge defenders -- and the continuity provided by manager Jose Mourinho in the dugout, it's logical Chelsea are stronger this season."