A man was reportedly hit from behind while a gang of five men tried to steal his MP3 player.
The assault happened on the playing field in Barleythorpe Road, Oakham, at about 3.15pm on Tuesday.
The victim was left with a minor injury to his face.
Oakham beacon officer PC Joe Lloyd, who is investigating the incident, is appealing to witnesses to come forward with any information they may have.
Call 101 quoting crime number LR/00561/13-1.