he was born in gouda and grew up in liempde. from 2002 to 2004, he was in the development team of the cycling team. de kort had a promising amateur career with wins in the under 23 version of paris–roubaix. in 2005 he became professional with the protour team of manolo saiz. that year he won a stage in the 2005 tour de l'avenir. in 2007 de kort joined the team. following the positive tests for heterologous blood doping by team members alexander vinokourov and andrey kashechkin, astana did not have much chance to compete in 2007 and was limited in 2008. speaking to dutch media, de kort expressed his frustrations at not having the chance to compete after being in a similar situation in 2006 with the liberty serguros team. he left astana at the end of the 2008 season, and joined the team.