Henry Milstrey had denied the charge during his trial in a Newark courtroom, but changed his plea "because I just can't take the chance. I wanted to tell my story and I think I did that," The (Newark) Star-Ledger reported Wednesday.
Milstrey pleaded to a lesser charge of third-degree aggravated assault. Had he been convicted of the second-degree offense, he would have faced up to 10 years in prison.
Milstrey argued with umpire Robert Kevin Waters in June 2011 after Water refused his request to call the game on account of darkness.
After the game was completed, Milstrey and Waters got into a fight. As many as 16 youths who had nothing to do with the game attacked and beat Waters.
Waters claimed Milstrey called the youths over. Milstrey said he didn't know any of them and he tried to pull them off the umpire.
Waters suffered a fractured skull, lost two teeth and lost some hearing in his left ear.
The former coach said he agreed to the plea because he felt jurors "weren't going to separate what those guys did from me."
Milstrey has seven children. He said his 11-year-old son, who was in the game, no longer plays baseball.