SAN ANTONIO — Spurs star Tim Duncan has filed a lawsuit contending that a series of investments enriched his financial adviser but were losing propositions for the NBA star, including $7.5 million in an entertainment company run by the adviser.

The lawsuit, filed Thursday in San Antonio, seeks more than $1 million in damages against Charles Banks of Atlanta. It claims Banks secretly withheld 20 percent of the return on Duncan’s loan to Gameday Entertainment, for which Banks serves as chairman.

The suit also alleges that Duncan’s signature was forged on at least two investment documents.

KENS-TV in San Antonio reports Duncan discovered the discrepancies last year while accounting for his assets as part of financial filings. Attempts to reach Banks for comment Friday were unsuccessful.