Premier League clubs were well represented at Borussia Dortmund's Champions League clash with Marseille.
The Daily Express says Chelsea were joined by Manchester City and Aston Villa in sending scouts to the tie.
Reports in France suggest that Chelsea were particularly interested in two players: Dortmund's Robert Lewandowski and Marseille's Florian Thauvin.
It is less clear who City and Villa were there to observe, although the Citizens are keen admirers of German international attacker Marco Reus and Paul Lambert's side have previously been credited with an interest in Marseille's Mathieu Valbuena.
