After finishing with the Burevestnik football academy in Yoshkar-Ola, he moved to his first adult football team in summer 1990-FC Stal Cheboksary, from the Soviet Second League B. As a seventeen-year-old, he was only able to make two appearances in the season.
At Tekstilshchik, Filimonov quickly established himself as first-team keeper and played his first European club tournament matches in 1994 in the UEFA Cup, against FC Nantes and Békéscsaba.