De Mul (born 4 March 1986) came to the Ajax youth academy from Belgian club Germinal Beerschot Antwerpen in 2002. A year later, on 1 July 2003, the Belgian player signed his first contract. He made his debut for Ajax 1 on 25 January 2004, in the match Ajax - NEC Nijmegen (1-0). He scored his first goal in the away match against FC Twente (2-3) on 15 August 2004. The winger played the 2005-2006 season on loan for Vitesse. De Mul played 52 matches in Ajax 1 in which he scored 5 goals.