The trial was originally scheduled to start Tuesday. The defense requested a delay but the reason wasn't immediately known. The delay until Feb. 27 was announced Wednesday.
Cox is charged with sexual assault against a person who was physically helpless and sexual assault against a person who was incapable of determining the nature of the conduct.
He has pleaded not guilty and is free on $50,000 bail.
Prosecutors say the woman was assaulted in September 2010. An arrest warrant affidavit says she became pregnant and that DNA tests indicate Cox is the father.
The Broncos waived Cox last month, citing his on-field performance.