Chicago police are investigating an accusation that Cubs shortstop Starlin Castro sexually assaulted a woman last fall. No charges have been filed at this time and Castro's representatives deny the allegation. WBBM Newsradio reports that the unidentified woman, who is in her 20s, was at a River North nightclub Sept. 29 when she met Castro. After 3 a.m. CT, she went with a friend to his apartment, where she alleges that the assault took place. The woman went to a hospital the next evening and police became involved, while Castro left for his offseason in the Dominican Republic.