Mikki Avelon Leander van Sas was born on 29 February 2004 in the Netherlands, making him a leap-year birthday holder. He began his footballing journey at local club USV Hercule before moving to the FC Utrecht academy in 2016, where he developed into a promising goalkeeper. In 2020, at just 16 years old, he made the step up to join Manchester City's academy setup in England.
Without breaking into City's first team, van Sas sought regular playing time and returned to the Netherlands in September 2023, joining Feyenoord. His time at the Rotterdam club yielded a notable honour: a Johan Cruyff Shield winners' medal in 2024. He then spent the 2024–25 season on loan at Vitesse, gaining further senior experience.
A composed, shot-stopping goalkeeper who is comfortable with the ball at his feet, van Sas signed permanently for EFL League One side Wycombe Wanderers on 28 June 2025, representing a fresh chapter in his career at senior level in English football.
At international level, van Sas has represented the Netherlands at youth level, receiving his first call-up to the Dutch Under-19 side in 2022. He made his debut for that age group on 21 September 2022 in a match against Moldova Under-19s. Wycombe Wanderers will be looking to him as a key part of their squad as they compete in League One.