A big pre-season victory for Seattle Seahawks cornerback Brandon Browner -- who will NOT be prosecuted for allegedly attacking his baby mama's father last month ... TMZ Sports has learned.
We broke the story ... cops were investigating Browner after the alleged victim claimed he was in a heated argument with the NFL player, who became violent. Browner allegedly left the scene in his white Bentley before cops arrived.
But according to new court docs obtained by TMZ Sports, the investigation hit a major roadblock -- because officials could not locate or interview Browner ... and the witnesses suddenly became uncooperative.
The L.A. County District Attorney's office ultimately decided they didn't have the goods to get a conviction -- and declined to move forward with charges.