Justin Gimelstob -- an ex-tennis star and current broadcaster -- pled not guilty to felony aggravated battery after he was accused of beating the hell out of a man during a trick-or-treating run on Halloween.
Gimelstob -- a former doubles champ who coaches tennis stud John Isner -- was arrested on the suspicion of roughing up a guy named Randall Kaplan while the man was trick-or-treating with his family in L.A. on Oct. 31.
In a restraining order Kaplan filed in November, he claims the tennis coach hit him from behind, pinned him down, punched him "more than 50 times" in the face and head and threatened to "f**king kill" him.
Justin showed up in court Wednesday in L.A. to face the battery with serious bodily injury charge -- a felony -- and pled not guilty.
If convicted, Gimelstob faces up to 4 years in prison AND a fine of up to $10,000.
While dealing with his case, Justin has reportedly taken a leave of absence from his role as an analyst at the Tennis Channel.
Gimelstob is due back in court in January.