The newspaper reported Monday that Daniel "Ponytail" Harris testified he was a passenger in the same SUV as 26-year-old Willie Clark when Clark allegedly started shooting into Williams' limousine.
Clark is on trial on first-degree murder and other charges. He maintains he is innocent and his attorneys have argued investigators should have targeted Harris in Williams' death.
Harris reached a plea agreement in a federal drug case in exchange for his testimony against Clark.
Authorities say the shooting happened after Williams and other football players got into an altercation at a Denver nightclub with another group that included Clark.