Napoli defender Kalidou Koulibaly has extended his contract until 2021, the Italian Serie A club said on their website on Monday. The Senegal international joined the Naples-based club in 2014 from Racing Genk. The 25-year-old, who has made four league appearances this season, was strongly linked with a move to Premier League Chelsea during the last transfer window. Napoli, top of the standings, travel to seventh-placed Genoa on Wednesday. (For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)