Hillen recently moved to Raków Czestochowa, a Polish club, but is still under contract with NAC Breda until the summer of 2029. The left-back joined NAC Breda in the summer of 2025 for a reported 300,000 euros, after spending time at De Graafschap, Jong Ajax, and AZ's youth academy. VoetbalPrimeur reports that Hillen understands why NAC Breda accepted a lower offer for him, as there were other clubs interested in signing him. According to Hillen, "Er zijn clubs die graag spelers willen halen en nu waren er wat clubs die voor mij wilden komen. Dat hoort erbij."