Frosler started his career as a winger in the Bidvest Wits academy before being converted to the full-back position by coach Gavin Hunt. He made 11appearances in his debut season during which he helped the club win its first ever PSL title. Ahead of the 2018–19 campaign, Frosler reportedly refused a new contract with Wits which resulted in him being frozen out at the club. By the half-way mark of the season, he had not played a single minute of football and signed a pre-contract with the club's rivals, Kaizer Chiefs.