Attorney Stephanie Rickard, who is representing Elissa Ennis, told the Sacramento Bee that she lied to police when she accused Foster of physically assaulting her on Feb. 11, the newspaper reported Tuesday.
Last week, Foster pleaded not guilty to felony domestic violence and weapons charges stemming from an incident involving Ennis three months ago. The preliminary trial is set for Thursday.
Foster is facing charges for domestic violence, forcefully attempting to prevent a victim from reporting a crime and possessing an assault weapon. Those charges were filed on April 12.
The Santa Clara County District Attorney's office initial accounting of the events of Feb. 11 alleged that Foster dragged Ennis by the hair, punched her in the head eight to 10 times and physically removed her from the house.
However, Rickard said Ellis' injuries, including a ruptured eardrum that sent her client to the hospital, were sustained in a fight with another woman. She also claimed there is a video of that confrontation to confirm her claim.
"(Foster) did not strike her, injure her or threaten her," Rickard said in a statement. The statement claims that Ennis' injuries "were the result of a physical fight with another woman, and that Foster tried to end his relationship with Ennis after he learned of the fight.
"She was extremely upset and told him if he broke up with her she would 'trash his career.'"
The district attorney's office now faces the dilemma of whether to continue the case against Foster if Ennis recants her initial accusations and testifies that she lied. Ennis could also face prosecution by acknowledging she made up the charges.
49ers general manager John Lynch said the team is prepared to release Foster if the charges are proven to be true.
Foster is also subject to possible NFL discipline under the league's personal conduct policy. The league mandates a six-game suspension for a first-time domestic violence offense.
Foster, a first-round draft pick (No. 31 overall) in 2017, started all 10 games in which he played last season as a rookie.