Sillamaa debuted for Estonian side
Kalev at the age of fifteen years-old in 2020. He went on to appear in 45 matches in the Estonian Premium League for the club, scoring four goals and providing five assists. He joined Belgian club
KAA Gent in July 2023, agreeing to a two-year professional contract having also had trials in Italy with Cagliari, SPAL and Napoli. He made his league debut for
Jong KAA Gent appearing as a second-half substitute in the 60th minute in a 1–0 victory against
Royal Cappellen in the
Belgian Division 1. He suffered a broken ankle shortly after the beginning of the 2024–25 season. This ruled him out of action for three months. He subsequently joined Slovak
2. Liga club
FC ŠTK 1914 Šamorín in January 2025. He made his debut for the club against
Zilina II in a 2–1 league victory on 3 March 2025. ==International career==