The plainclothes police officer who tackled the retired tennis player James Blake to the sidewalk during an arrest in Manhattan last month used excessive force, according to an investigation by the Civilian Complaint Review Board, New York City’s independent agency for police misconduct.

In a letter sent to Mr. Blake’s lawyer on Tuesday, the board said it had completed its investigation into the conduct of the officer, James Frascatore, during the arrest on Sept. 9 in front of the Grand Hyatt Hotel on 42nd Street in Midtown. The officer’s actions, recorded on surveillance video, prompted outrage and happened amid a national conversation over the proper use of force by the police.

The board substantiated the charge of excessive force against Officer Frascatore and recommended the stiffest punishment: departmental charges that could lead to suspension or dismissal.

He will now face an internal Police Department trial; the police commissioner, William J. Bratton, has the final say on discipline of officers.