The letter to Blake from the Civilian Complaint Review Board, dated Oct. 6, says that charges of excessive force and abuse of authority were both substantiated.
Blake was tossed to the ground outside a Midtown hotel last month as he waited to be picked up to go to the U.S. Open by an officer looking for someone else. He suffered cuts and bruises in the incident, which was captured on video, and during which he was held down by several officers.
The CCRB recommended disciplinary action for abuse of authority for one of the officers and charges for use of force for the other, according to the document.
Commissioner Bill Bratton apologized to Blake at the time.
"I want to express my appreciation to the Civilian Complaint Review Board for their quick and thorough review of the incident during which I was attacked on September 9, 2015," Blake said in a statement. "I have complete respect for the principle of due process and appreciate the efforts of the CCRB to advance this investigation."
The NYPD said it was aware of the CCRB's findings and that the department's internal review is ongoing.