A local junior, Mestrov made his first-grade debut for Manly-Warringah in Round 12, 1990 against the Gold Coast Seagulls, coming off the bench in a 34–0 victory at Brookvale Oval.
In 1994, Mestrov signed for South Sydney. Mestrov was a part of the Souths team which won that year's pre-season Tooheys Challenge Cup. Mestrov played in the final in which they defeated the Brisbane Broncos 27–26 at Albury.[3]
Mestrov played one further season for Souths before departing at the end of 1995 to move to England and take up a contract with the London Broncos. He later signed with Wigan after leaving London at the end of 1997.