Dufek’s single-seater debut followed productive years in karting at the very young age of eight years old. The years thereafter, he kept impressing and registering strong results. Quickly recognised as a talented driver, Joshua joined the prestigious Sauber Junior Team in 2019. As a Sauber Junior driver, he performed very well during the closing stages of his karting career, claiming respectable results in top level race events such as the WSK Euro Series and the CIK-FIA World Championship.