The defender has made seven appearances for Chelsea since joining from Strasbourg last summer, including one in our triumphant FIFA Club World Cup campaign.

Earlier this year, Sarr started for Senegal as they defeated Morocco 1-0 in the Africa Cup of Nations final. He was also involved in their squad for this summer's FIFA World Cup.

We wish Mamadou well in the Basque Country and look forward to monitoring his progress throughout the season.